Co-reporter:Wei Xia, Chong Qu, Zibin Liang, Bote Zhao, Shuge Dai, Bin Qiu, Yang Jiao, Qiaobao Zhang, Xinyu Huang, Wenhan Guo, Dai Dang, Ruqiang Zou, Dingguo Xia, Qiang Xu, and Meilin Liu
Nano Letters May 10, 2017 Volume 17(Issue 5) pp:2788-2788
Publication Date(Web):April 10, 2017
DOI:10.1021/acs.nanolett.6b05004
Metal oxides and carbon-based materials are the most promising electrode materials for a wide range of low-cost and highly efficient energy storage and conversion devices. Creating unique nanostructures of metal oxides and carbon materials is imperative to the development of a new generation of electrodes with high energy and power density. Here we report our findings in the development of a novel graphene aerogel assisted method for preparation of metal oxide nanoparticles (NPs) derived from bulk MOFs (Co-based MOF, Co(mIM)2 (mIM = 2-methylimidazole). The presence of cobalt oxide (CoOx) hollow NPs with a uniform size of 35 nm monodispersed in N-doped graphene aerogels (NG-A) was confirmed by microscopic analyses. The evolved structure (denoted as CoOx/NG-A) served as a robust Pt-free electrocatalyst with excellent activity for the oxygen reduction reaction (ORR) in an alkaline electrolyte solution. In addition, when Co was removed, the resulting nitrogen-rich porous carbon–graphene composite electrode (denoted as C/NG-A) displayed exceptional capacitance and rate capability in a supercapacitor. Further, this method is readily applicable to creation of functional metal oxide hollow nanoparticles on the surface of other carbon materials such as graphene and carbon nanotubes, providing a good opportunity to tune their physical or chemical activities.Keywords: Metal−organic framework; N-doped graphene aerogel; ORR catalyst; supercapacitor;
Co-reporter:Hang Wei, Zhonghong Xia, and Dingguo Xia
ACS Applied Materials & Interfaces December 20, 2017 Volume 9(Issue 50) pp:43657-43657
Publication Date(Web):December 1, 2017
DOI:10.1021/acsami.7b13468
The exploration of anode materials of lithium-ion batteries (LIBs) is still a great challenge because of their low electrical conductivity and poor durability. Transition-metal oxides are proposed as a potential alternative, even though their dimension and structure greatly affect their electrochemical properties. In this study, MnO/Mn2SiO4@C cuboids were prepared via the polymerization–pyrolysis process. Larger MnCO3 precursor particles embedded into a monolithic carbon framework and formed smaller nanoparticles owing to the inducing effect of Si element in phthalocyanino silicon (SiPc), giving MnO/Mn2SiO4@C cuboids. The micron-scaled cuboid composite can lead to higher tap density and greater electrical performance due to lower interparticle resistance. Therefore, the as-prepared MnO/Mn2SiO4@C electrode exhibits stable specific capacities of 585.9 and 423.9 mA h g–1 after 1000 discharge/charge cycles at 1 and 2 A g–1, respectively. Meanwhile, an excellent rate capacity of 246.3 mA h g–1 was achieved even at 30 A g–1. Additionally, this facile and economical strategy to improve electrode performance provides a commercially feasible way for the construction of high-performance LIBs.Keywords: anodes; cuboids; induced; lithium-ion batteries; MnO/Mn2SiO4@C;
Co-reporter:Huijun Yan, Biao Li, Zhen Yu, Wangsheng Chu, and Dingguo Xia
The Journal of Physical Chemistry C April 6, 2017 Volume 121(Issue 13) pp:7155-7155
Publication Date(Web):March 14, 2017
DOI:10.1021/acs.jpcc.7b01168
Lithium-rich layered oxides (LLOs) are promising cathode materials for next-generation lithium ion batteries with high energy density. However, the charge cutoff potential of 4.8 V constrains seriously the actual application of LLOs. Herein, using density functional theory (DFT) calculation, we investigated the tuning mechanism of chlorine doping on the redox potential and redox process in LLOs. The results showed that chlorine doping can decrease the charge potential, modulate the ratio of two redox couples of cation and anion, and lower the band gap of LLOs. These tunings were beneficial for the modification of the safety, cycling stability, and voltage decay of LLOs materials. This work opens up a new route in terms of performance improvement via tuning of redox behavior based on deep understanding of anion doping mechanism.
Co-reporter:Biao Li, Huijun Yan, Yuxuan Zuo, and Dingguo Xia
Chemistry of Materials April 11, 2017 Volume 29(Issue 7) pp:2811-2811
Publication Date(Web):February 28, 2017
DOI:10.1021/acs.chemmater.6b04743
Recently, more and more new high-capacity lithium-rich layered oxides involving both metal and oxygen redox have been proposed. However, the structural stability was influenced by the irreversible oxygen redox, which leads to the instability of the oxygen framework. Here, we propose that the reversibility of the oxygen redox in Li2RuO3 can be controlled by tuning its electronic structure via incorporating boron atoms into the interstitial sites of the Li2RuO3 layered structure and obtain higher-stability lithium-rich layered oxides. Using in situ X-ray diffraction and X-ray absorption fine structure, we conclude that oxygen redox was tuned to a reversible level without reduction of Ru as reported previously. The intrinsic mechanism of the modification was further determined by density functional theory calculations. This work will provide a new scope for the strategy of balancing the high capacity and good structural stability of lithium-rich layered oxides.
Co-reporter:Hang Wei, Zhonghong Xia, and Dingguo Xia
ACS Applied Materials & Interfaces 2017 Volume 9(Issue 8) pp:
Publication Date(Web):February 6, 2017
DOI:10.1021/acsami.6b15820
A uniform anode material composed of ultrasmall tin oxide (SnO2) nanoparticles with an excellent lithium-ion (Li-ion) storage performance is obtained for the first time through one step UV curing technology. The diameter of ∼3 nm-sized SnO2 particles is uniformly dispersed in the styrylpyridinium (SbQ) polymer because of its photo-cross-linking property. The in situ cross-linking of SbQ polymer not only assist synthesis of uniform ultrasmall SnO2, but act as a strong adhesion binder on SnO2 nanoparticles, thereby effectively accommodating the volume expansion of SnO2 anodes during cycling process. The uniform electrode exhibits substantially higher specific capacity and longer cycling stability compared with the SnO2 nanoparticles electrodes treated by traditional PVDF-mixing method. A stable specific capacity of 572.5 mA h g–1 of the SnO2 electrode derived from UV curing technology is obtained at a current density of 0.2 C (156.2 mA g–1) after 150 cycles. Even at high rate of 5 C (3905 mA g–1), the electrode still demonstrates specific capacity of 440.2 mA h g–1. Therefore, the scalable and low-cost synthetic approach described herein can readily be extended to other nanomaterials electrodes to improve their lithium-storage properties.Keywords: lithium ion battery; one step; SnO2 electrode; ultrafine nanoparticle; UV curing technology;
Co-reporter:Biao Li
Advanced Materials 2017 Volume 29(Issue 48) pp:
Publication Date(Web):2017/12/01
DOI:10.1002/adma.201701054
AbstractThe extraordinarily high capacities delivered by lithium-rich oxide cathodes, compared with conventional layered oxide electrodes, are a result of contributions from both cationic and anionic redox processes. This phenomenon has invoked a lot of research exploring new kinds of lithium-rich oxides with multiple-electron redox processes. Though proposed many years ago, anionic redox is now regarded to be crucial in further developing high-capacity electrodes. A basic overview of the previous work on anionic redox is given, and issues related to electronic and geometric structures are discussed, including the principles of activation, reversibility, and the energy barrier of anionic redox. Anionic redox also leads to capacity loss and structural degradation, as well as voltage hysteresis, which shows the importance of controlling anionic redox reactions. Finally, the techniques used for characterizing anionic redox processes are reviewed to aid the rational choice of techniques in future studies. Important perspectives are highlighted, which should instruct future work concerning anionic redox processes.
Co-reporter:Weifeng Huang;Augusto Marcelli
Advanced Energy Materials 2017 Volume 7(Issue 21) pp:
Publication Date(Web):2017/11/01
DOI:10.1002/aenm.201700460
AbstractThe search for superior-energy-density electrode materials for rechargeable batteries is prompted by the continuously growing demand for new electric vehicles and large energy-storage grids. The structural properties of electrode materials affect their electrochemical performance because their functionality is correlated to their structure at the atomic scale. Although challenging, a deeper and comprehensive understanding of the basic structural operating units of electrode materials may contribute to the advancement of new energy-storage technologies and many other technologies. Therefore, we must strategically control both the structure and kinetics of electrode materials to achieve optimal electrochemical performance. In this contribution, advancements in synchrotron radiation techniques, specifically in situ/operando experiments on electrode materials for rechargeable batteries, are presented and discussed. Indeed, the latest synchrotron radiation methods offer deeper insights into pristine and chemically modified electrode materials, opening new opportunities to optimize these materials and exploit new technologies. In particular, the most recent results from in situ/operando synchrotron radiation measurements, which play a critical role in the fundamental understanding of the kinetics processes that occur in rechargeable batteries, are discussed.
Co-reporter:Biao Li;Ruiwen Shao;Huijun Yan;Li An;Bin Zhang;Hang Wei;Jin Ma;Xiaodong Han
Advanced Functional Materials 2016 Volume 26( Issue 9) pp:1330-1337
Publication Date(Web):
DOI:10.1002/adfm.201504836
Lithium-rich layered oxides are considered as promising cathode materials for Li-ion batteries with high energy density due to their higher capacity as compared with the conventional LiMO2 (e.g., LiCoO2, LiNiO2, and LiNi1/3Co1/3Mn1/3O2) layered oxides. However, why lithium-rich layered oxides exhibit high capacities without undergoing a structural collapse for a certain number of cycles has attracted limited attention. Here, based on the model of Li2RuO3, it is uncovered that the mechanism responsible for the structural integrity shown by lithium-rich layered oxides is realized by the flexible local structure due to the presence of lithium atoms in the transition metal layer, which favors the formation of O22−-like species, with the aid of in situ extended X-ray absorption fine structure (EXAFS), in situ energy loss spectroscopy (EELS), and density functional theory (DFT) calculation. This finding will open new scope for the development of high-capacity layered electrodes.
Co-reporter:Hang Wei, Jin Ma, Biao Li, Li An, Junli Kong, Pingrong Yu and Dingguo Xia
NPG Asia Materials 2016 8(3) pp:e255
Publication Date(Web):2016-03-01
DOI:10.1038/am.2016.29
The nanostructure and the dimension of materials greatly affect their performance and function. It is important to develop synthesis strategies that enable the control of the materials’ morphology and structure and further reduce their size. In the present work, we report a novel synthesis approach that utilizes Si nanoparticles for synthesizing ultrafine MnO nanowires. The resulting nanostructure comprises MnO nanowires with a diameter of ~5–10 nm embedded in an amorphous carbon matrix. X-ray diffraction patterns and high-resolution transmission electron microscopy images clearly reveal the growth mechanism of nanowires. As an anode material for the lithium-ion battery, the nanostructure exhibits excellent charge transfer kinetics and extremely high electrochemical performance, including reversible specific capacities of 285.9 mA h g−1 at 30 A g−1 and 757.4 mA h g−1 at 1 A g−1 after 1000 cycles. X-ray absorption fine structure (XAFS) confirms that the enhanced performance is related to the increase of the ordering of the O2− ions in the MnO structure during the charge/discharge processes. This novel synthesis strategy may inspire studies of other transition-metal-oxide nanomaterials with special orientation to tune their physical chemistry properties.
Co-reporter:Li An, Zhonghong Xia, Peikai Chen, and Dingguo Xia
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 43) pp:29536
Publication Date(Web):October 12, 2016
DOI:10.1021/acsami.6b10793
Transition metal oxynitrides have now garnered growing interest in our quest for highly efficient alternatives to Pt in direct methanol alkaline fuel cells. Herein, carbon supported Co3Mo2OxN6–x was synthesized via a simple two-step approach wherein the reactants undergo refluxing and heat treatment in NH3. For the as-prepared Co3Mo2OxN6–x catalyst, uniformly dispersed on XC-72, with the particle size averaged at 5 nm, the catalytic activities toward oxygen reduction reaction in alkaline media are related to the commercial Pt/C, such as the comparable onset potential (0.9 V vs RHE), half-wave potential (0.8 V vs RHE), and even higher specific activity (82.7 mA cm–2 at 0.7 V). Significantly, the Co3Mo2OxN6–x catalyst was highly stable in terms of 95% current retention after 12 h chronoamperometry measurement, indicative of favorable prospect for the non-noble cathodic catalyst in alkaline fuel cell.Keywords: alkaline fuel cell; catalyst; Co3Mo2OxN6−x /C; layered transition metal oxynitride; oxygen reduction reaction
Co-reporter:Xin Chen, Junbo Chang, Huijun Yan, and Dingguo Xia
The Journal of Physical Chemistry C 2016 Volume 120(Issue 51) pp:28912-28916
Publication Date(Web):December 7, 2016
DOI:10.1021/acs.jpcc.6b08560
The oxygen reduction reaction (ORR) catalytic mechanism and activity on B12N12 and B60N60 nanocages were investigated in detail by density functional theory methods. The calculated results indicate that all the adsorption energies of ORR intermediates on B12N12 are close to those known for the Pt(111) catalyst, implying that it can be an effective catalyst for the ORR, with catalytic properties similar to Pt. A relative energy profile suggests that the ORR process could spontaneously take place on the studied two BN nanocages, with a four-electron reduction mechanism. More importantly, during the entire reduction process, the BN nanocages can provide dual-catalytic sites, especially in the second and third H transfer step, further accelerating the ORR pathways. Thus, the synergistic catalytic effect between B and N atoms is demonstrated to be considerable in BN nanocages.
Co-reporter:Jin Ma
The Journal of Physical Chemistry C 2016 Volume 120(Issue 25) pp:13421-13426
Publication Date(Web):June 8, 2016
DOI:10.1021/acs.jpcc.6b04338
Si-doped layered manganese-based lithium-rich oxides were used as cathodes for lithium-ion batteries. The silicon-doped electrode exhibits exceptional specific capacity as well as rate capability compared to those of the pristine sample. In particular, the modified cathode shows noticeable enhancement in thermal stability, wherein the heat release is reduced and the position of the exothermic peak increases by 60 °C. First-principles calculations suggest that Si atoms occupy sites of transition metals in Si-doped Li-rich materials, which gives rise to an appreciable downshift of the O 2p band relative to that of the pristine sample.
Co-reporter:Yingxiang Peng, Lufang Cui, Shifeng Yang, Jingjing Fu, Lirong Zheng, Yi Liao, Kai Li, Xia Zuo, Dingguo Xia
Electrochimica Acta 2015 Volume 154() pp:102-109
Publication Date(Web):1 February 2015
DOI:10.1016/j.electacta.2014.12.081
Metal-phthalocyanine (MPc) macrocyclic catalysts have been perceived as promising alternatives to Pt and Pt-based catalysts for the oxygen reduction reaction (ORR). However, the effect of different MPc molecular structures on the ORR has rarely been reported in depth. Herein, iron-phthalocyanine polymers (poly-FePcs) and multi-walled carbon nanotubes (MWCNTs) composites with different structures were synthesized using microwave method. The relationship between their molecular structure and electrocatalytic activity was fully revealed by density functional theory (DFT) and X-ray fine absorption spectroscopy (XAFS). DFT calculations revealed that the introduction of halogen atoms can increase the ion potential (IP) and the dioxo-binding energy () of the poly-FePcs. Meanwhile, their conjugated structure not only facilitates electronic transmission, but also significantly increases . XAFS analysis indicated that the poly-FePc/MWCNTs composites had a square planar structure and a smaller of phthalocyanine ring (Fe-N4 structure) skeleton structure radius when a larger conjugated structure or introduced halogen atoms was present. The experimental results suggest that the these changes in properties arising from the different structures of the MPc macrocyclic compounds led to a huge effect on their ORR electrochemical activities, and provide a guide to obtaining promising electrochemical catalysts.
Co-reporter:Xin Chen
The Journal of Physical Chemistry C 2015 Volume 119(Issue 21) pp:11493-11498
Publication Date(Web):May 4, 2015
DOI:10.1021/acs.jpcc.5b02505
The oxygen reduction reaction mechanisms catalyzed by B, N doped α- and γ-graphyne were investigated in detail by DFT methods, in which doped graphynes with different configurations could exhibit different oxygen reduction reaction activities. The B or N single-doped α-B1G and α-N2G and co-doped α-B1N2G and α-B1N3G show relatively low catalytic activities, owing to their unfavorable reversible potential in oxygen reduction steps, while the co-doped α-B1N4G with separated B, N and single-doped γ-NG show relatively high activities. With the further increasing of the N content, the onset potential is largely enhanced to 0.413 V for α-B1(N4)3G. The origin of activity of α-B1(N4)3G and γ-NG is attributed to the higher energy levels of the highest occupied molecular orbital and/or more positive charge (spin) density distributions.
Co-reporter:Li An, Huijun Yan, Biao Li, Jin Ma, Hang Wei, Dingguo Xia
Nano Energy 2015 Volume 15() pp:24-32
Publication Date(Web):July 2015
DOI:10.1016/j.nanoen.2015.03.031
•We have firstly synthesized the supported intermetallic N-PtTe nanoparticles.•The high activity and durability toward formic acid oxidation is superior to Pt/C.•The synergetic effects between Pt and Te enhance the activity and durability.The insufficient durabilities and low catalytic activities of formic acid oxidation electrocatalysts have prohibited the practical application of formic acid fuel cells. Herein, we prepare ordered intermetallic-phase N–PtTe nanoparticles with high electrocatalytic activity and superior durability towards formic acid electro-oxidation. The enhanced catalytic activity and stability are mainly attributed to the synergetic effects of atomic Pt and Te on the particle surfaces, in which Te helps to activate OH− and allows Pt to easily oxidize the CO⁎ intermediate species to CO2. The present work highlights the mechanism of activity enhancement towards formic acid electro-oxidation after the incorporation of Te, which is desirable for the design of intermetallic electrocatalysts and potential applications in low temperature fuel cells.
Co-reporter:Dr. Weifeng Huang;Dr. Biao Li;Muhammad Farooq Saleem; Xiang Wu;Dr. Jianjian Li;Jun Lin;Wangsheng Chu; Ziyu Wu
Chemistry - A European Journal 2015 Volume 21( Issue 2) pp:851-860
Publication Date(Web):
DOI:10.1002/chem.201403062
Abstract
A series of alluaudite Na2Fe3−xMnx(PO4)3 microcompounds, which self-assembled from primary nanorods, were prepared successfully through a solvothermal method. As a promising candidate cathode for sodium-ion batteries, it is necessary to obtain a deeper understanding of the relationship between the structure and physicochemical properties of these materials. The local electronic and geometric environments were systematically investigated, for the first time, by using a combination of soft/hard X-ray absorption, IR, and Mössbauer spectroscopy. The results show that the electrochemical performance is not only associated with morphology, but also with the electronic and crystalline structure. With the introduction of manganese into the lattice, the long-range order maintains the isostructural framework and the lattice parameters expand as expected. However, for short-range order, PO4 tetrahedra and MO6 octahedra (M=Fe and Mn) become more severely distorted as a function of Mn concentration. Meanwhile, larger MnO6 octahedra will compress the space of FeO6 octahedra, which will result in stronger core/electron–electron interactions for Fe, as characterized by hard/soft X-ray absorption spectra. These slight changes in the electronic and local structures lead to different electrochemical performances with changes to the manganese content. Moreover, other physicochemical properties, such as magnetic behavior, are also confirmed to be correlated with these different electron interactions and local geometric environments.
Co-reporter:Nanlin Zhang
The Journal of Physical Chemistry C 2015 Volume 119(Issue 2) pp:907-912
Publication Date(Web):December 18, 2014
DOI:10.1021/jp510108r
Bimetallic catalysts exhibit a promising prospect as potential alternative catalysts for oxygen reduction reaction because of their distinctively enhanced activities compared to pure monometallic systems. Understanding of the origin of activity enhancement is essential for exploiting any novel bimetallic catalyst. In this work, we used AuCu3 as a model to study the synergetic effects existing among the atoms with strong and weak affinity toward oxygen through density functional theory (DFT) calculation. The results suggest that the combination site of Au and Cu instead of Au–Au or Cu–Cu site provided the best onset potential (0.75 V vs reversible hydrogen electrode (RHE)) for oxygen reduction reaction, which is very close to what has been achieved on Pt(111). And the narrow gap between the onset potentials of AuCu3 and Pt obtained by calculation is consistent with the experimental result. Such results not only explain synergetic effects on bimetallic alloy but also may shed light on designing a novel catalyst for ORR.
Co-reporter:Zhihui Yu;Yanna Kou;Ying Dai;Xiayan Wang;Hang Wei
Electrocatalysis 2015 Volume 6( Issue 4) pp:341-347
Publication Date(Web):2015 July
DOI:10.1007/s12678-015-0249-y
Biocompatible materials with large specific surface areas can play a crucial role in direct electron transfer between redox proteins and an electrode surface. Here, we report zirconium phosphate–carbon aerogel (ZrP-CA) composites with a large specific surface area and uniform nanopore distributions as matrix for glucose oxidase immobilization. The immobilized glucose oxidase displays two stable, well-defined redox peaks with an electron transfer rate constant of 9.34 s−1 in nitrogen-saturated phosphate-buffered saline (PBS) solution (0.1 M, pH 7.0), at a scan rate of 100 mV s−1. The modified electrode was also used as a glucose biosensor, which was found to exhibit a linear calibration range of 0.12–2.0 mM, sensitivity of 5.56 μA mM−1 cm−2 at an applied potential of −0.5 V, and detection limit of 34 μM based on a signal-to-noise ratio of 3. After 80 scan cycles, the decreases in the peak current were less than 8 %, indicating good stability of the as-prepared ZrP-CA. The unique characteristics of the ZrP-CA nanocomposite make it a good matrix for protein immobilization and biosensor preparation.
Co-reporter:Biao Li;Huijun Yan;Jin Ma;Pingrong Yu;Weifeng Huang;Wangsheng Chu;Ziyu Wu
Advanced Functional Materials 2014 Volume 24( Issue 32) pp:5112-5118
Publication Date(Web):
DOI:10.1002/adfm.201400436
Lithium-rich manganese-based layered oxides show great potential as high-capacity cathode materials for lithium ion batteries, but usually exhibit a poor cycle life, gradual voltage drop during cycling, and low thermal stability in the highly delithiated state. Herein, a strategy to promote the electrochemical performance of this material by manipulating the electronic structure through incorporation of boracic polyanions is developed. As-prepared Li[Li0.2Ni0.13Co0.13Mn0.54](BO4)0.015(BO3)0.005O1.925 shows a decreased M-O covalency and a lowered O 2p band top compared with pristine Li[Li0.2Ni0.13Co0.13Mn0.54]O2. As a result, the modified cathode exhibits a superior reversible capacity of 300 mA h g−1 after 80 cycles, excellent cycling stability with a capacity retention of 89% within 300 cycles, higher thermal stability, and enhanced redox couple potentials. The improvements are correlated to the enhanced oxygen stability that originates from the tuned electronic structure. This facile strategy may further be extended to other high capacity electrode systems.
Co-reporter:Li An, Weifeng Huang, Nanlin Zhang, Xin Chen and Dingguo Xia
Journal of Materials Chemistry A 2014 vol. 2(Issue 1) pp:62-65
Publication Date(Web):25 Oct 2013
DOI:10.1039/C3TA13877A
Carbon-supported CoN (CoN/C) nanoparticles have been synthesized by heating at reflux in the solution of o-xylene and subsequent thermal annealing under a NH3 reducing atmosphere. The as-prepared CoN/C composite exhibited high oxygen reduction reaction (ORR) activity and excellent stability as a new efficient non-precious metal electrocatalyst.
Co-reporter:Hang Wei, Jin Ma, Biao Li, Yuxuan Zuo, and Dingguo Xia
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 22) pp:20276
Publication Date(Web):October 2, 2014
DOI:10.1021/am505807k
High energy density Li–S batteries are highly attractive. However, their use in practical applications has been greatly affected by their poor cycle life and low rate performance, which can be partly attributed to the dissolution of polysulfides from the S cathode and their migration to the Li anode through the separator. While much effort has been devoted to designing the structure of the S cathodes for suppressing the dissolution of polysulfides, relatively little emphasis has been placed on modifying the separator. Herein, we demonstrate a new approach for modifying the separator with a polyvinylidene fluoride-carbon (PVDF-C) layer, where the polysulfides generated in the Li–S cells can be localized on the cathode side. Li–S batteries based on the novel separator and a cathode prepared by the simple mixing of a S powder and super P have delivered discharge capacities of 918.6 mAh g–1, 827.2 mAh g–1, and 669.1 mAh g–1 after 100, 200, and 500 cycles, respectively, at a discharge rate of 0.5 C. Even under current densities of up to 5 C, the cells were able to retain a discharge capacity of 393 mAh g–1, thereby demonstrating an excellent high rate performance and stability. The exceptional electrochemical performance could be attributed to the intense adsorption capability of the micropores, presence of C–C double bonds, and conductivity of the C network in the PVDF-C layer. This economical and simple strategy to overcome the polysulfide dissolution issues provides a commercially feasible method for the construction of Li–S batteries.Keywords: high-performance lithium sulfur battery; modified separator; PVDF-C layer
Co-reporter:Rui Zhang, Yingxiang Peng, Zhipan Li, Kai Li, Jie Ma, Yi Liao, Lirong Zheng, Xia Zuo, Dingguo Xia
Electrochimica Acta 2014 Volume 147() pp:343-351
Publication Date(Web):20 November 2014
DOI:10.1016/j.electacta.2014.09.064
Multi-walled carbon nanotubes (MWCNTs) supported iron phthalocyanine (FePc), binuclear iron phthalocyanine (bi-FePc) and iron polyphthalocyanine (FePPc) were prepared by a solvothermal process. The resulting FePc/MWCNTs, bi-FePc/MWCNTs and FePPc/MWCNTs were heat-treated in argon (Ar) atmosphere at various temperatures ranging from 500 to 900 °C to obtain optimized catalysts for the oxygen reduction reaction (ORR). The crystal structure, morphology and chemical environment of the catalysts were examined by ultraviolet-visible (UV–Vis) spectroscopy, X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure spectroscopy (XAFS). The electrocatalytic activity of the obtained catalysts was measured using a rotating disk electrode (RDE) technique in 0.5 mol L−1 H2SO4 solution saturated with oxygen. The ORR activity of the heat-treated FePPc/MWCNTs was found to be better than that of the heat-treated bi-FePc/MWCNTs and FePc/MWCNTs. Furthermore, the heat-treatment temperature greatly influenced the catalytic ORR ability of the catalysts. The FePPc/MWCNTs heat-treated at 800 °C exhibited a four-electron transfer process and the best ORR activity (EORR = 0.79 V vs. RHE), methanol resistance, and stability (current loss = 13% at –0.13 V vs. Hg/Hg2SO4 after 55 h). XPS indicated that pyridine-type nitrogen, not graphitic-N, played a critical role in determining the electrocatalytic ORR activity of the amples. XAFS showed that the coordination geometry around Fe was close to square planar in structure, suggesting that the Fe-N4 structure was produced by the high temperature treatment.
Co-reporter:Wang ZhenYao, Li Biao, Ma Jin, Xia DingGuo
Electrochimica Acta 2014 Volume 117() pp:285-291
Publication Date(Web):20 January 2014
DOI:10.1016/j.electacta.2013.11.124
Nanocrystalline Li[Li0.26Ni0.11Mn0.63]O2 were easily prepared by using Ni0.15Mn0.85(OH)2 and Li2CO3 as precursors and KCl as melt-salt for the high capacity materials of Li-ion storage. The obtained nanoparticles showed same morphology of polygonal shape and the particle size distribution increased with increasing sinter temperature. The Li[Li0.26Ni0.11Mn0.63]O2 electrode sintered at 800 °C for 12 h exhibits a reversible capacity of more than 300 mAh g−1 at 0.1 C rate between 2 V and 4.8 V and the capacity retention remains 86% and 90% after 90 cycles at the rate of 0.5 C and 1 C, respectively. These superior electrochemical performances are discussed in detail and ascribed to the low dimension and well-crystallized particles. The low dimension provides a short diffusion path and fast transport channels for the lithium ion insertion/extraction reactions and the well-crystallized structure restrains the elimination of oxide ion vacancies and metal ions rearrangement during charge–discharge cycling.
Co-reporter:Xiuyun Zhao, Dingguo Xia, Juncheng Yue, Shuzhen Liu
Electrochimica Acta 2014 Volume 116() pp:292-299
Publication Date(Web):10 January 2014
DOI:10.1016/j.electacta.2013.10.196
A novel C/Fe3C composite prepared by simple polymerization-pyrolysis of iron phthalocyanine (PcFe) at 700 °C in an Ar atmosphere, exhibits a high reversible capacity, stable cyclability, excellent rate performance, improved initial efficiency and reduced hysteresis as an anode material for lithium ion batteries. In-situ embedded Fe3C nanoparticles and N doping can enhance electrical conductivity and facilitate the reaction of C/Fe3C electrode effectively. This work provides a new way for developing high performance non-graphitic carbon electrode materials in the future.
Co-reporter:Wang ZhenYao, Li Biao, Ma Jin and Xia DingGuo
RSC Advances 2014 vol. 4(Issue 30) pp:15825-15829
Publication Date(Web):10 Feb 2014
DOI:10.1039/C3RA47044J
A nanocrystalline lithium-rich cathode material (Li[Li0.26Ni0.11Mn0.63]O2) has been prepared by a molten salt method. By using KCl–NaCl as the reaction media, the synthetic temperature can be reduced to 700 °C. The prepared material was investigated using XRD, SEM and galvanostatic charge–discharge cycling, and shows highly crystallized shapes with average particle sizes of 50–100 nm. Due to its low dimensional, highly-crystalline and regularly shaped layered structure, the cathode material exhibits greatly improved capability and cycling performance when compared with the pristine cathode.
Co-reporter:Xin Chen;Xiaoming Hu;Li An;Nanlin Zhang;Xia Zuo
Electrocatalysis 2014 Volume 5( Issue 1) pp:68-74
Publication Date(Web):2014 January
DOI:10.1007/s12678-013-0164-z
The electrochemical reduction approach has been suggested as a promising method for detoxification of chlorine-containing aromatic hydrocarbons. In this study, the electrocatalytic dechlorination of atrazine was studied by using a non-noble catalyst, binuclear iron phthalocyanine coated onto multi-walled carbon nanotubes (bi-FePc/MWNT). Both experimental and theoretical results indicate that dechlorination of atrazine occurs rapidly on bi-FePc/MWNT electrode. The reaction depends on the adsorption of the chlorinated organic compound on the electrode surface and the reaction rate with hydroxy. By liquid chromatography–tandem mass spectrometer technique, the dechlorination product of atrazine can be assigned to 2-hydroxy-4-ethylamino-6-isopropylamino-1,3,5-triazine, which could be disposed by more convenient and economic biodegradation method.
Co-reporter:Huaifang Shang, Wangsheng Chu, Jie Cheng, Fangfang Pan, Dongming Cheng, Dingguo Xia, Wenlou Wang and Ziyu Wu
Journal of Materials Chemistry A 2013 vol. 1(Issue 22) pp:6635-6641
Publication Date(Web):22 Mar 2013
DOI:10.1039/C3TA10390K
Despite the great achievement in understanding the materials properties of LiFePO4, the surface phase composition of nanosized LiFePO4 has been almost ignored. The present study reports the synthesis of nanosized core–shell LiFePO4 with size of about 50 nm by one step solvothermal route using Polyethylene glycol 600 as solvent. The structural characterization of the surface of nanosized core–shell LiFePO4 particles has been investigated using soft X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy. The nanosized LiFePO4 is well-covered by an amorphous LiFeP2O7 layer containing trace carbon. Density functional theory (DFT) calculation is used to illustrate the origin of amorphous LiFeP2O7 layer. The nanosized core–shell LiFePO4 exhibits excellent charge transfer kinetics and charge/discharge performance. These new investigations shed new insight into the surface phase composition of nano-particles. The synthesis of the nanosized core–shell LiFePO4 paves an effective way to develop cathode materials with high rate capabilities for use in Li-ion batteries.
Co-reporter:Xiaoming Hu, Dingguo Xia, Lei Zhang, Jiujun Zhang
Journal of Power Sources 2013 Volume 231() pp:91-96
Publication Date(Web):1 June 2013
DOI:10.1016/j.jpowsour.2012.12.018
High crystallinity binuclear iron phthalocyanine coated onto multi-walled carbon nanotubes (bi-FePc/MWNT), was synthesized. Transmission electron microscopy (TEM) confirms that the crystalline bi-FePc forms a uniform coating on the carbon nanotubes with a thickness of about 20 nm. The plane of the macrocyle is perpendicular to the surface of the nanotube and the stacking axis of the bi-FePc molecules, which is the direction of high electrical conductivity, is found to be parallel to the substrate. The bi-FePc/MWNT show activity of 1.43 mA cm−2 at 0.66 V versus NHE indicating good activity and the current is stable for 14 h as electrocatalyst in oxygen reduction reactions (ORR) indicating good stability; the oxygen reduction current does not change in the presence of methanol showing the binuclear iron phthalocyanine coated onto multi-walled carbon nanotubes specifically catalyzes oxygen reduction and not methanol oxidation.Highlights► High crystallinity binuclear iron phthalocyanine was synthesized. ► The bi-FePc/MWNT catalyst exhibits a superior electrochemical performance. ► The stacking axis of the bi-FePc molecules is parallel to the substrate.
Co-reporter:Xin Chen, Fan Li, Nanlin Zhang, Li An and Dingguo Xia
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 44) pp:19330-19336
Publication Date(Web):01 Oct 2013
DOI:10.1039/C3CP52802B
Fe(Co)–Nx/C is an important candidate catalyst for the next generation proton exchange membrane fuel cells (PEMFC), but the relationship between the structure and the oxygen reduction activity is still unclear. In this work, the different active site structures of Fe(Co)–Nx/C are explored and the oxygen reduction catalytic mechanisms are studied by means of density functional theory (DFT). Different kinds of Me–Nx/C motifs, including the edge site around the graphene sheet and the internal site in the graphene sheet (as well as in the graphyne sheet), are constructed and investigated. The calculated results suggest that for the edge active sites, high O2 adsorption strength may result in direct oxidation of metal ions thus losing their catalytic activity. The internal active sites are stable in acidic solution and display catalytic ability of oxygen reduction. The catalytic activity of the internal site is affected by three factors: the kind of internal metal ion, the bonded nitrogen or carbon atoms with metal ions and the size of the graphene sheet.
Co-reporter:Bin Qiu, Xiuyun Zhao, Dingguo Xia
Journal of Alloys and Compounds 2013 Volume 579() pp:372-376
Publication Date(Web):5 December 2013
DOI:10.1016/j.jallcom.2013.05.148
•CoS2/RGO was in situ synthesized by employing graphene oxides as oxidizer and Na2S2O3 as reductor.•The CoS2 particles of 150 nm were uniformly dispersed on the RGO nanosheets.•The enhanced properties can be attributed to the small particle size and the RGO networks.This study reports a novel strategy of preparing CoS2/reduced graphene oxides (RGO) nanocomposites by employing graphene oxides (GO) as an oxidizing agent and Na2S2O3 as a reducing agent. CoS2 can be in situ synthesized with GO being reduced. X-ray diffraction (XRD), Raman spectrometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical test are used to characterize the nanocomposite. The CoS2 particles with the size of 150 nm are dispersed in the networks made from thin RGO nanosheets. The CoS2/RGO nanocomposite as an anode material for lithium-ion batteries can deliver excellent reversible capacity retention (640 mA hg−1) after cycling 50 times when tested at 100 mA g−1 and rate performance. The enhanced electrochemical properties can be attributed to the nanoscale particles sizes of CoS2 in addition to the effects of RGO networks in preventing the agglomeration of CoS2 and absorbing lithium polysulfides during the charge-discharge processes.
Co-reporter:Chuanhao Yao, Fan Li, Xiang Li and Dingguo Xia
Journal of Materials Chemistry A 2012 vol. 22(Issue 32) pp:16560-16565
Publication Date(Web):25 Jun 2012
DOI:10.1039/C2JM32866F
We report on the successful synthesis of fiber-like nanostructured Ti4O7 (NS-Ti4O7) by multistep method. The specific surface area of this NS-Ti4O7 was 26 m2 g−1. The synthesized NS-Ti4O7 was platinized and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS) and electrochemical testing. It was found that the monodispersed Pt nanoparticles supported on NS-Ti4O7 with a uniform size of 4.8 nm. The prepared Pt/NS-Ti4O7 catalysts exhibited superior durability as well as enhanced Pt mass activity in comparison to commercial Pt/XC-72 catalyst. After undergoing accelerated durability tests (ADT), the oxygen reduction reaction (ORR) mass activity of Pt/NS-Ti4O7 was nearly thirty times higher than that of Pt/XC-72. The superior durability of Pt/NS-Ti4O7 is attributed to the high stability of Ti4O7 and the strong metal–support interaction between Pt and Ti4O7.
Co-reporter:Xiang Li, Li An, Xiayan Wang, Fan Li, Ruqiang Zou and Dingguo Xia
Journal of Materials Chemistry A 2012 vol. 22(Issue 13) pp:6047-6052
Publication Date(Web):16 Feb 2012
DOI:10.1039/C2JM16504J
Supported chemically ordered Pt–Fe intermetallic compounds have been prepared through a straightforward two-stage approach. By taking advantage of this straightforward two-stage synthesis, we have for the first time successfully obtained supported Pt3Fe1 and Pt1Fe1 intermetallic nanoparticles with a mean size of less than 5 nm, a narrow size distribution and good dispersion. The nanoparticles of supported intermetallic Pt3Fe1 and Pt1Fe1 compounds showed superior electrocatalytic activities towards the oxygen reduction reaction (ORR). The ORR enhancement in supported electrocatalysts made from Pt–Fe intermetallic compounds may be attributed to their geometric and electronic structure. Accelerated durability tests (ADT) show that Pt3Fe1/C has better durability, the electrochemical surface area (ECSA) values of commercial Pt/C decreased by 49% after 5000 cycles, but Pt1Fe1/C showed a reduction in the ECSA value of 3% after 5000 cycles.
Co-reporter:Xiuyun Zhao, Dingguo Xia, and Kun Zheng
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 3) pp:1350
Publication Date(Web):February 2, 2012
DOI:10.1021/am201617j
A plum pudding-like Fe3O4/Fe/carbon composite was synthesized by a sol–gel polymerization followed by a heat-treatment process and characterized by X-ray diffraction, Raman spectroscopic analysis, thermogravimetric analysis, scanning electron microscopy with energy-dispersive spectroscopy, transmission electron microscopy, and electrochemical test. In this composite, uniform spherical Fe3O4/Fe nanoparticles of about 100 nm were embedded into carbon matrix with high monodispersion. As-prepared Fe3O4/Fe/carbon composite electrode exhibits a stable and reversible capacity of over 600 mA h g–1 at a current of 50 mA g–1 between 0.002 V and 3.0 V, as well as excellent rate capability. The plum pudding-like structure, in which trace Fe promotes conductivity and carbon matrix mediates the volume change, can enhance the cycling performance and rate capability of Fe3O4 electrode. This unique structure is valuable for the preparation of other electrode materials.Keywords: anode material; Fe3O4/Fe/carbon composite; lithium ion battery; plum pudding-like structure;
Co-reporter:Juncheng Yue, Xiuyun Zhao, Dingguo Xia
Electrochemistry Communications 2012 Volume 18() pp:44-47
Publication Date(Web):2012
DOI:10.1016/j.elecom.2012.02.001
A novel C/Co composite with Co nanoparticles embedded in carbon matrix is synthesized firstly by pyrolysis of polymeric cobalt phthalocyanine (PcCo) at 700 °C in argon atmosphere. This composite is investigated as an anode material for lithium ion batteries, indicating high tap density and excellent electrochemical performance. The C/Co electrode can retain a higher reversible capacity of over 600 mAh g− 1 at a current of 50 mA g− 1 after 40 cycles and shows better rate capability and less hysteresis in comparison to carbon not containing Co. The significant improvement is attributed to the Co nanoparticles grown in-situ reaction with catalytic activity and high electrical conductivity.Highlights► A novel C/Co composite with high tap density is synthesized firstly by pyrolysis of polymeric phthalocyanine cobalt. ► Co nanoparticles grown by in-situ reaction are embedded in carbon matrix homogeneously. ► The C/Co composite shows reduced hysteresis, high capacity and good rate capability as anode of lithium ion battery. ► Co nanoparticles enhance electric conductivity and catalyze the reaction of C/Co electrode effectively.
Co-reporter:Xiuyun Zhao, Dingguo Xia, Kun Zheng
Journal of Alloys and Compounds 2012 Volume 513() pp:460-465
Publication Date(Web):5 February 2012
DOI:10.1016/j.jallcom.2011.10.081
An Fe3O4–FeO–Fe@C composite material has been successfully synthesized by a one-pot hydrothermal method without any templates and a sequential heat treatment process. X-ray diffraction, Raman spectrometry, scanning electron microscopy with energy dispersive spectroscopy, transmission electron microscopy and galvanostatic cell cycling have been used to characterize the structure and electrochemical performance of the as-prepared Fe3O4–FeO–Fe@C composite. The electrode shows a stable and reversible capacity of over 600 mAh g−1 at a current of 53 mA g−1 for up to 60 cycles, which could be ascribed to the unique double-layer core–shell and embedded structures.Highlights► An Fe3O4–FeO–Fe@C composite has been successfully synthesized. ► The Fe3O4–FeO–Fe@C composite has a unique double-layer core–shell structure and an embedded structure. ► Electrochemical performance of Fe3O4–FeO–Fe@C composite electrode has been investigated.
Co-reporter:Xin Chen, Shaorui Sun, Xiayan Wang, Fan Li, and Dingguo Xia
The Journal of Physical Chemistry C 2012 Volume 116(Issue 43) pp:22737-22742
Publication Date(Web):October 8, 2012
DOI:10.1021/jp307055j
A theoretical study on the oxygen reduction mechanism catalyzed by metal–polyaniline is investigated in detail by means of density functional theory. In the oxygen reduction process, we find that −OH, not H2O2, is the reaction intermediate. The catalytic activities for the studied models decrease in the sequence CoFe–PANI > Fe–PANI (FeFe–PANI) > Co–PANI. This is due to a synergistic effect between heterogeneous metal atoms in CoFe–PANI, which facilitates additional electron donation from the active sites to the adsorbed oxygen reduction intermediates. The doping with cobalt may also decrease the HOMO–LUMO gap in CoFe–PANI, making it more active.
Co-reporter:Xin Chen, Fan Li, Xiayan Wang, Shaorui Sun, and Dingguo Xia
The Journal of Physical Chemistry C 2012 Volume 116(Issue 23) pp:12553-12558
Publication Date(Web):May 23, 2012
DOI:10.1021/jp300638e
A theoretical study of the oxygen reduction mechanism catalyzed by cobalt–polypyrrole is investigated in detail by means of density functional theory method using the BLYP/DZP basis set. The calculations suggest that the cobalt–polypyrrole has a platinum-like catalytic behavior based on the adsorption energetics of the reaction intermediates. The di-cobalt–polypyrrole catalyst exhibits a higher catalytic activity than that of mono-cobalt–polypyrrole, due to the fact that the PPy chains in di-cobalt–polypyrrole have a regular structure.
Co-reporter:Lijuan Zhang, Pu Hu, Xiuyun Zhao, Ruili Tian, Ruqiang Zou and Dingguo Xia
Journal of Materials Chemistry A 2011 vol. 21(Issue 45) pp:18279-18283
Publication Date(Web):13 Oct 2011
DOI:10.1039/C1JM12990B
The present study reports a straightforward template-free route for the synthesis of core–shell Co@CoO nanocomposites by the controlled reduction of Co3O4 nanospheres. The target Co@CoO nanoparticles consist of an unsealed hollow porous CoO shell with a metal Co core, in which the outer porous CoO shell as the active anode material can be fully in contact with the electrolyte. The void within the particles provides a remarkable buffer to tolerate volume changes of the electrode materials during the insertion and extraction of lithium. Most importantly, the inner nanosized metal Co core gives a new impetus to the reversible decomposition of Li2O due to its catalytic activity. Furthermore, the exposed metal Co portion outside the nanoshells provides a favorable electrical contact between adjacent particles and greatly improves the efficiency of the electronic connection between the active material and the current collector. The Co@CoO nanocomposite maintains an excellent reversible capacity over 800 mA h g−1 after 50 cycles with an initial coulombic efficiency of 74.2%, which is much higher than that of pure CoO (67.8%). This superior electrochemical performance is closely related to the unique composition and nanostructure of the electrode material. Notably, it is the first case of a hybrid-structured Co@CoO anode material derived from the reduction process from oxide precursors. Such a conclusion may be advantageously used to guide the design of a wide range of nanostructured metal oxides.
Co-reporter:Shaorui Sun ; Ning Jiang
The Journal of Physical Chemistry C 2011 Volume 115(Issue 19) pp:9511-9517
Publication Date(Web):April 26, 2011
DOI:10.1021/jp101036j
In this paper, density functional theory is applied to study the electrochemical reduction of oxygen on iron phthalocyanine (FePc), iron porphyrin (FeP), cobalt phthalocyanine (CoPc), and cobalt porphyrin (CoP). According to the calculation results, for the four metal−macrocyclic complexes, O2 will not directly be cleaved without the cooperation of hydrogen. In the reduction process, on FePc or FeP, H2O2 does not form as an intermediate, and O2 is reduced to H2O, while on CoPc or CoP, O2 is just reduced to H2O2. The reason why the oxygen reduction ability of FePc or FeP is higher than that of CoPc or CoP, respectively, is that the energy level of the highest-occupied 3d orbital of the former is higher than that of the later. The high energy level of the metal 3d orbital leads to the strong ability of oxygen reduction.
Co-reporter:Xiuyun Zhao, Zhonghong Xia, Dingguo Xia
Electrochimica Acta 2010 Volume 55(Issue 20) pp:6004-6009
Publication Date(Web):1 August 2010
DOI:10.1016/j.electacta.2010.05.056
Sn/Cu nanowire composite film was electrodeposited on copper foil substrates and used as an anode material for lithium-ion batteries. The structure of the obtained composite film anode was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical performance was evaluated by cyclic voltammetry, galvanostatic cycling and impedance spectroscopy. It was found that the Sn/Cu nanowire composite film anode showed a better cycle stability than Sn film anode, whereas the Sn/CNT composite film anode indicated poor capacity retention. It could be deduced that copper nanowire reinforced the Sn film anode due to the better wetting property of Sn on the surface of copper and reduced the loss of electric contact among tin particles in the Sn/Cu nanowire composite film anode.
Co-reporter:Xiuyun Zhao, Dingguo Xia, Lin Gu, Juncheng Yue, ... Jixue Li
Journal of Energy Chemistry (May 2014) Volume 23(Issue 3) pp:291-300
Publication Date(Web):1 May 2014
DOI:10.1016/S2095-4956(14)60150-9
Silicon is being investigated extensively as an anodic material for next-generation lithium ion batteries for portable energy storage and electric vehicles. However, the large changes in volume during cycling lead to the breakdown of the conductive network in Si anodes and the formation of an unstable solid-electrolyte interface, resulting in capacity fading. Here, we demonstrate nanoparticles with a Si@Mn22.6Si5.4C4@C double-shell structure and the formation of self-organized Si-Mn-C nanocomposite anodes during the lithiation/delithiation process. The anode consists of amorphous Si particles less than 10 nm in diameter and separated by an interconnected conductive/buffer network, which exhibits excellent charge transfer kinetics and charge/discharge performances. A stable specific capacity of 1100 mAh·g−1 at 100 mA·g−1 and a coulombic efficiency of 99.2% after 30 cycles are achieved. Additionally, a rate capacity of 343 mAh·g−1 and a coulombic efficiency of 99.4% at 12000 mA·g−1 are also attainable. Owing to its simplicity and applicability, this strategy for improving electrode performance paves a way for the development of high-performance Si-based anodic materials for lithium ion batteries.A Si@Mn22.6Si5.4C4@C composite with a double-shelled structure is developed and used to form a self-organized nanocomposite Si anode in lithium ion batteries, exhibiting much improved cycling performance and excellent rate capability.Download full-size image
Co-reporter:Dongtang Zhang; Fuxiang Wu; Manhua Peng; Xiayan Wang; Dingguo Xia;Guangsheng Guo
Journal of the American Chemical Society () pp:
Publication Date(Web):May 1, 2015
DOI:10.1021/jacs.5b01088
Ordered intermetallic nanomaterials are of considerable interest for fuel cell applications because of their unique electronic and structural properties. The synthesis of intermetallic compounds generally requires the use of high temperatures and multiple-step processes. The development of techniques for rapid phase- and size-controlled synthesis remains a formidable challenge. The intermetallic compound Pt1Bi2 is a promising candidate catalyst for direct methanol fuel cells because of its high catalytic activity and excellent methanol tolerance. In this work, we explored a one-step, facile and ultrafast phase- and size-controlled process for synthesizing ordered Pt–Bi intermetallic nanoparticles (NPs) within seconds in microfluidic reactors. Single-phase Pt1Bi1 and Pt1Bi2 intermetallic NPs were prepared by tuning the reaction temperature, and size control was achieved by modifying the solvents and the length of the reaction channel. The as-prepared Pt–Bi intermetallic NPs exhibited excellent methanol tolerance capacity and high electrocatalytic activity. Other intermetallic nanomaterials, such as Pt3Fe intermetallic nanowires with a diameter of 8.6 nm and Pt1Sn1 intermetallic nanowires with a diameter of 6.3 nm, were also successfully synthesized using this method, thus demonstrating its feasibility and generality.
Co-reporter:Xin Chen, Fan Li, Nanlin Zhang, Li An and Dingguo Xia
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 44) pp:NaN19336-19336
Publication Date(Web):2013/10/01
DOI:10.1039/C3CP52802B
Fe(Co)–Nx/C is an important candidate catalyst for the next generation proton exchange membrane fuel cells (PEMFC), but the relationship between the structure and the oxygen reduction activity is still unclear. In this work, the different active site structures of Fe(Co)–Nx/C are explored and the oxygen reduction catalytic mechanisms are studied by means of density functional theory (DFT). Different kinds of Me–Nx/C motifs, including the edge site around the graphene sheet and the internal site in the graphene sheet (as well as in the graphyne sheet), are constructed and investigated. The calculated results suggest that for the edge active sites, high O2 adsorption strength may result in direct oxidation of metal ions thus losing their catalytic activity. The internal active sites are stable in acidic solution and display catalytic ability of oxygen reduction. The catalytic activity of the internal site is affected by three factors: the kind of internal metal ion, the bonded nitrogen or carbon atoms with metal ions and the size of the graphene sheet.
Co-reporter:Lijuan Zhang, Pu Hu, Xiuyun Zhao, Ruili Tian, Ruqiang Zou and Dingguo Xia
Journal of Materials Chemistry A 2011 - vol. 21(Issue 45) pp:NaN18283-18283
Publication Date(Web):2011/10/13
DOI:10.1039/C1JM12990B
The present study reports a straightforward template-free route for the synthesis of core–shell Co@CoO nanocomposites by the controlled reduction of Co3O4 nanospheres. The target Co@CoO nanoparticles consist of an unsealed hollow porous CoO shell with a metal Co core, in which the outer porous CoO shell as the active anode material can be fully in contact with the electrolyte. The void within the particles provides a remarkable buffer to tolerate volume changes of the electrode materials during the insertion and extraction of lithium. Most importantly, the inner nanosized metal Co core gives a new impetus to the reversible decomposition of Li2O due to its catalytic activity. Furthermore, the exposed metal Co portion outside the nanoshells provides a favorable electrical contact between adjacent particles and greatly improves the efficiency of the electronic connection between the active material and the current collector. The Co@CoO nanocomposite maintains an excellent reversible capacity over 800 mA h g−1 after 50 cycles with an initial coulombic efficiency of 74.2%, which is much higher than that of pure CoO (67.8%). This superior electrochemical performance is closely related to the unique composition and nanostructure of the electrode material. Notably, it is the first case of a hybrid-structured Co@CoO anode material derived from the reduction process from oxide precursors. Such a conclusion may be advantageously used to guide the design of a wide range of nanostructured metal oxides.
Co-reporter:Xiang Li, Li An, Xiayan Wang, Fan Li, Ruqiang Zou and Dingguo Xia
Journal of Materials Chemistry A 2012 - vol. 22(Issue 13) pp:NaN6052-6052
Publication Date(Web):2012/02/16
DOI:10.1039/C2JM16504J
Supported chemically ordered Pt–Fe intermetallic compounds have been prepared through a straightforward two-stage approach. By taking advantage of this straightforward two-stage synthesis, we have for the first time successfully obtained supported Pt3Fe1 and Pt1Fe1 intermetallic nanoparticles with a mean size of less than 5 nm, a narrow size distribution and good dispersion. The nanoparticles of supported intermetallic Pt3Fe1 and Pt1Fe1 compounds showed superior electrocatalytic activities towards the oxygen reduction reaction (ORR). The ORR enhancement in supported electrocatalysts made from Pt–Fe intermetallic compounds may be attributed to their geometric and electronic structure. Accelerated durability tests (ADT) show that Pt3Fe1/C has better durability, the electrochemical surface area (ECSA) values of commercial Pt/C decreased by 49% after 5000 cycles, but Pt1Fe1/C showed a reduction in the ECSA value of 3% after 5000 cycles.
Co-reporter:Li An, Weifeng Huang, Nanlin Zhang, Xin Chen and Dingguo Xia
Journal of Materials Chemistry A 2014 - vol. 2(Issue 1) pp:NaN65-65
Publication Date(Web):2013/10/25
DOI:10.1039/C3TA13877A
Carbon-supported CoN (CoN/C) nanoparticles have been synthesized by heating at reflux in the solution of o-xylene and subsequent thermal annealing under a NH3 reducing atmosphere. The as-prepared CoN/C composite exhibited high oxygen reduction reaction (ORR) activity and excellent stability as a new efficient non-precious metal electrocatalyst.
Co-reporter:Huaifang Shang, Wangsheng Chu, Jie Cheng, Fangfang Pan, Dongming Cheng, Dingguo Xia, Wenlou Wang and Ziyu Wu
Journal of Materials Chemistry A 2013 - vol. 1(Issue 22) pp:NaN6641-6641
Publication Date(Web):2013/03/22
DOI:10.1039/C3TA10390K
Despite the great achievement in understanding the materials properties of LiFePO4, the surface phase composition of nanosized LiFePO4 has been almost ignored. The present study reports the synthesis of nanosized core–shell LiFePO4 with size of about 50 nm by one step solvothermal route using Polyethylene glycol 600 as solvent. The structural characterization of the surface of nanosized core–shell LiFePO4 particles has been investigated using soft X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy. The nanosized LiFePO4 is well-covered by an amorphous LiFeP2O7 layer containing trace carbon. Density functional theory (DFT) calculation is used to illustrate the origin of amorphous LiFeP2O7 layer. The nanosized core–shell LiFePO4 exhibits excellent charge transfer kinetics and charge/discharge performance. These new investigations shed new insight into the surface phase composition of nano-particles. The synthesis of the nanosized core–shell LiFePO4 paves an effective way to develop cathode materials with high rate capabilities for use in Li-ion batteries.
Co-reporter:Chuanhao Yao, Fan Li, Xiang Li and Dingguo Xia
Journal of Materials Chemistry A 2012 - vol. 22(Issue 32) pp:NaN16565-16565
Publication Date(Web):2012/06/25
DOI:10.1039/C2JM32866F
We report on the successful synthesis of fiber-like nanostructured Ti4O7 (NS-Ti4O7) by multistep method. The specific surface area of this NS-Ti4O7 was 26 m2 g−1. The synthesized NS-Ti4O7 was platinized and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS) and electrochemical testing. It was found that the monodispersed Pt nanoparticles supported on NS-Ti4O7 with a uniform size of 4.8 nm. The prepared Pt/NS-Ti4O7 catalysts exhibited superior durability as well as enhanced Pt mass activity in comparison to commercial Pt/XC-72 catalyst. After undergoing accelerated durability tests (ADT), the oxygen reduction reaction (ORR) mass activity of Pt/NS-Ti4O7 was nearly thirty times higher than that of Pt/XC-72. The superior durability of Pt/NS-Ti4O7 is attributed to the high stability of Ti4O7 and the strong metal–support interaction between Pt and Ti4O7.
