Co-reporter:Xiuxia Lin, Xiufang Wang, Ligui Li, Mingfang Yan, and Yong Tian
ACS Sustainable Chemistry & Engineering November 6, 2017 Volume 5(Issue 11) pp:9709-9709
Publication Date(Web):September 29, 2017
DOI:10.1021/acssuschemeng.7b01398
Mechanical grinding is exploited to effectively rupture biomass cotton microfibers into metal-free, nitrogen-doped carbon nanosheets with a large number of mesoporous textures. Experimentally, raw microfibers of absorbent cotton are presoaked with fuming sulfuric acid to generate plenty of hierarchical pores/cavities, which sufficiently expose the inner parts of cotton microfibers to nitrogen source for efficient incorporation of nitrogen dopants onto carbon skeletons in subsequent thermal annealing process. Mechanical grinding of these thermally annealed carbon microfibers leads to exfoliated nitrogen-doped thin carbon nanosheets with a high surface area of 912.1 m2/g as well as abundant mesopores and a considerable nitrogen content of 8.5 at. %. These characteristics contribute to an excellent electrocatalyst with marked catalytic activities toward oxygen reduction reaction in an alkaline electrolyte solution, including a more positive half-wave potential, much higher diffusion-limiting current, remarkably enhanced operation stability, and stronger immunity against fuel-crossover effects, as compared to commercial Pt/C catalysts. The present results provide a novel facile method to the scalable preparation of biomass-derived highly porous two-dimensional carbons for efficient electrochemical energy devices.Keywords: Cotton microfiber; Mechanical grinding; Mesoporous carbon nanosheet; Nitrogen doping; Oxygen reduction reaction;
Co-reporter:Dengke Zhao, Ligui Li, Wenhan Niu, Shaowei Chen
Sensors and Actuators B: Chemical 2017 Volume 243() pp:380-387
Publication Date(Web):May 2017
DOI:10.1016/j.snb.2016.12.018
•P3HT films with high electrical conductivity were facilely prepared by HAuCl4 doping.•The HAuCl4-doped P3HT film could be easily dedoped by volatile amines and thiols vapors.•Associated color and conductivity variation of P3HT during dedoping was significant.•Sensitive logic gates for selectively sensing of amines and thiols using HAuCl4-doped P3HT.Highly conductive polythiophene films with electrical conductivity of 71.7 S/cm were prepared by using a facile solution-processing method with HAuCl4 as a dopant. The density of free charge carriers for thus-prepared polythiophene films was estimated to be 4.48 × 1021/cm3. In addition, upon doping, the color of the polymer films changed significantly with the main absorption peaks bathochromically shifted from the visible to near-infrared region. Interestingly, the polythiophene films could be easily dedoped when exposed to organic amines and thiols. The dual variations of film color and electrical conductivity thus were exploited for the design and fabrication of a logic circuit, in combination with polythiophene films doped by electrochemical oxidation, for selective detection of volatile amines and thiols with a detection limit lower than 1 ppm. The results demonstrate the high potential of this solution-doping method in the preparation of highly conducting organic thin films for vapor sensing.
Co-reporter:Yi Peng;Bingzhang Lu;Nan Wang;Shaowei Chen
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 14) pp:9336-9348
Publication Date(Web):2017/04/05
DOI:10.1039/C6CP08925A
Polymer electrolyte membrane fuel cells represent a next-generation power supply technology that may be used in a diverse range of applications. Towards this end, the rational design and engineering of functional nanomaterials as low-cost, high-performance catalysts is of critical significance in the wide-spread commercialization of fuel cell technology. One major bottleneck is the oxygen reduction reaction (ORR) at the cathode. Whereas platinum-based nanoparticles have been used as the catalysts of choice, further engineering of the nanoparticles is urgently needed to enhance the catalytic performance and concurrently reduce the costs. Extensive research has also been extended to non-platinum metals or even metal-free nanocatalysts that may be viable alternatives to platinum. In this review article, we will summarize recent progress in these areas of research within the context of interfacial electron transfer: (a) interactions between metal elements in alloy nanoparticles, (b) metal–ligand interfacial bonding interactions, (c) metal–carbon substrate interactions, and (d) heteroatom doping of graphitic carbons. Results have shown that ready manipulation of the electronic interactions between the catalyst surface and oxygen species may serve as a fundamental mechanism for the optimization of the catalytic performance.
Co-reporter:Jinghao Wu;Ji Liu;Xiufang Wang
Journal of Materials Science 2017 Volume 52( Issue 16) pp:9794-9805
Publication Date(Web):09 May 2017
DOI:10.1007/s10853-017-1165-8
Herein, we report a facile, bottom-up route to the preparation of N-doped carbons with a high surface area as well as plenty of hierarchical pores by thermal annealing the black bread-like sulfuric acid-dehydrated sucrose. This simple sulfuric acid treatment created a remarkable surface area of 645.7 m2/g in the dehydrated sucrose, and the subsequent thermal annealing with activated reagent ZnCl2 and nitrogen source NH4Cl helped further generated more porous textures in the carbon matrix, which contributes to a high surface area of 2450 m2/g, a large number of hierarchical pores ranging from 2 to 150 nm in a highly porous N-doped carbon to sufficiently expose active sites and boost mass transfer. The best sample N/PC-800, which was thermally annealed at 800 °C, is able to selectively catalyze the 4e− ORR process and shows higher working stability, stronger tolerance to methanol crossover effect, a very comparable onset potential and diffusion-limited current density in alkaline electrolyte, compared to the benchmark Pt/C catalyst. The results in this study signify the validity of present facile, robust template-free method in the synthesis of highly porous N-doped carbons for electrochemical energy conversion and storage.
Co-reporter:Shuaibo Zeng, Ligui Li, Lihong Xie, Dengke Zhao, Ni Zhou, Nan Wang, Shaowei Chen
Carbon 2017 Volume 122(Volume 122) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.carbon.2017.06.036
Lithium-sulfur batteries represent one of the next-generation Li-ion batteries; yet rapid performance degradation is a major challenge. Herein, a highly crosslinked copolymer is synthesized through thermally activated polymerization of sulfur and trithiocyanuric acid onto the surface of reduced graphene oxide nanosheets. Of the thus-synthesized composites, the sample with a high sulfur content of 81.79 wt.% shows a remarkable rate performance of 1341 mAh g−1 at 0.1 C and 861 mAh g−1 at 1 C with an almost 100% coulombic efficiency. The composite electrode also effectively impedes the dissolution of polysulfides and their shuttle diffusion because of the abundant and robust chemical bonding between sulfur and trithiocyanuric acid and spatial confinement of polysulfides by the reduced graphene oxide sheets, which leads to 81.72% retention of the initial capacity even after 500 deep charge-discharge cycles at 1 C, corresponding to a decay rate of only 0.0404% per cycle. This performance is markedly better than those of comparative materials prepared in a similar fashion but at either higher or lower S loading, and among the highest in sulfur copolymer cathodes to date. The results provide an effective paradigm in the preparation and engineering of polymer cathode materials for high-performance lithium-sulfur batteries.Download high-res image (330KB)Download full-size image
Co-reporter:Shuaibo Zeng, Ligui LiDengke Zhao, Ji Liu, Wenhan Niu, Nan Wang, Shaowei Chen
The Journal of Physical Chemistry C 2017 Volume 121(Issue 5) pp:
Publication Date(Web):January 13, 2017
DOI:10.1021/acs.jpcc.6b09543
Flexible polymers show high potential applications in rechargeable lithium–sulfur (Li–S) batteries for their capability of confining sulfur diffusion and tolerance to large volume expansion during lithiation. Herein, sulfur is copolymerized with 3-butylthiophene via radical polymerization by heating the mixture of both components at controlled temperatures. Further capping of the thus-synthesized copolymer CP(S3BT) with highly conductive PEDOT:PSS thin film substantially enhances the electrical conductivity. With the resulting polymer hybrids as the cathode material, a Li–S battery is constructed which shows an initial discharge capacity of 1362 mA h g–1 at 0.1 C and a reversible capacity of 631 mA h g–1 even at 5 C. Moreover, the polymer cathode exhibits a high capacity of 682 mA h g–1 after 500 charge–discharge cycles at 1 C with 99.947% retention per cycle. The remarkable performance is attributed to the synergetic effects of (i) high conductivity resulting from both the conducting blocks of poly(3-butylthiophene) (P3BT) and PEDOT:PSS capping layer, (ii) physical confinement of polysulfides by P3BT segments and PEDOT:PSS capping layers, and (iii) chemical confinement resulting from the high density of chemical bonds between sulfur and 3-butylthiophene. The results may offer a new paradigm in the development of efficient and stable polymer cathodes for high performance Li–S batteries.
Co-reporter:Wenhan Niu, Ligui Li, Nan Wang, Shuaibo Zeng, Ji Liu, Dengke Zhao and Shaowei Chen
Journal of Materials Chemistry A 2016 vol. 4(Issue 28) pp:10820-10827
Publication Date(Web):12 May 2016
DOI:10.1039/C6TA03570A
The electrocatalytic activity of nitrogen-doped carbons towards the oxygen reduction reaction is largely determined by the concentration of active nitrogen dopants and the electrochemically accessible surface area. Herein we report a novel, facile route for the preparation of N-doped carbons based on direct pyrolysis of polypyrrole nanosheet precursors synthesized by confining the polymerization on the surface of NaCl crystals using FeCl3 as both the initiator and dopant. In the heating-up process of pyrolysis, a large amount of homogeneously distributed FeCl3 dopant and its derivatives gradually evolved into volatile nanoparticles which helped to generate abundant hierarchical macro- and meso-pores, resulting in honeycomb-like porous carbons with a high content of nitrogen dopants ranging from 7 to 18 at%, a large surface area, and an ORR activity superior to that of commercial Pt/C in alkaline electrolytes. Significantly, by using the best sample that was prepared at 800 °C (HPC-800) as the air electrode, a Zn–air battery was found to display a specific capacity of 647 mA h g−1 at 10 mA cm−2 and a negligible loss of voltage even after continuous operation for 110 h, a performance markedly better than that with Pt/C as the air cathode. The results not only highlight the significance of precursor engineering in the synthesis of highly efficient nitrogen-doped carbon catalysts for oxygen electroreduction, but also suggest the high potential of the interfacially confined polymerization method in the scalable preparation of cost-effective, highly porous carbons for electrochemical energy storage and conversion devices.
Co-reporter:Ji Liu;Dr. Ligui Li;Wenhan Niu;Nan Wang;Dengke Zhao;Shuaibo Zeng;Dr. Shaowei Chen
ChemElectroChem 2016 Volume 3( Issue 7) pp:1116-1123
Publication Date(Web):
DOI:10.1002/celc.201600178
Abstract
Direct carbonization methods represent a facile strategy for the synthesis of functional carbon electrocatalysts, however, the resulting carbons are mostly microporous and of low surface area, which disfavor mass transfer, and usually have low electrocatalytic activity. In this study, a hydrogen-bonded organic framework (HOF) comprising of melamine and trimesic acid is used as a highly porous precursor to prepare N-doped carbons through facile, direct pyrolysis. The high nitrogen content of melamine and the intrinsically porous nature of the HOF facilitates the formation of a mesoporous carbon with 4.8 atom % content of nitrogen dopants and a significantly high surface area of 1321 m2 g−1. Electrochemical measurements show that the best sample, which was pyrolyzed at 800 °C (HOF-800), exhibited efficient catalytic activity for oxygen electroreduction in 0.1 m KOH aqueous solution. This catalyst exhibits a much more positive onset potential, higher diffusion-limited current density, higher electron-transfer number in the low overpotential region, higher stability, and stronger tolerance against methanol crossover than the state-of-the-art Pt/C catalysts. The results in this study suggest the potential of intrinsically porous HOFs for the development of highly efficient nonprecious-metal electrocatalysts.
Co-reporter:Wenhan Niu; Ligui Li; Xiaojun Liu; Nan Wang; Ji Liu; Weijia Zhou; Zhenghua Tang;Shaowei Chen
Journal of the American Chemical Society 2015 Volume 137(Issue 16) pp:5555-5562
Publication Date(Web):April 10, 2015
DOI:10.1021/jacs.5b02027
Thermally removable nanoparticle templates were used for the fabrication of self-supported N-doped mesoporous carbons with a trace amount of Fe (Fe-N/C). Experimentally Fe-N/C was prepared by pyrolysis of poly(2-fluoroaniline) (P2FANI) containing a number of FeO(OH) nanorods that were prepared by a one-pot hydrothermal synthesis and homogeneously distributed within the polymer matrix. The FeO(OH) nanocrystals acted as rigid templates to prevent the collapse of P2FANI during the carbonization process, where a mesoporous skeleton was formed with a medium surface area of about 400 m2/g. Subsequent thermal treatments at elevated temperatures led to the decomposition and evaporation of the FeO(OH) nanocrystals and the formation of mesoporous carbons with the surface area markedly enhanced to 934.8 m2/g. Electrochemical measurements revealed that the resulting mesoporous carbons exhibited apparent electrocatalytic activity for oxygen reduction reactions (ORR), and the one prepared at 800 °C (Fe-N/C-800) was the best among the series, with a more positive onset potential (+0.98 V vs RHE), higher diffusion-limited current, higher selectivity (number of electron transfer n > 3.95 at +0.75 V vs RHE), much higher stability, and stronger tolerance against methanol crossover than commercial Pt/C catalysts in a 0.1 M KOH solution. The remarkable ORR performance was attributed to the high surface area and sufficient exposure of electrocatalytically active sites that arose primarily from N-doped carbons with minor contributions from Fe-containing species.
Co-reporter:Nan Wang, Wenhan Niu, Ligui Li, Ji Liu, Zhenghua Tang, Weijia Zhou and Shaowei Chen
Chemical Communications 2015 vol. 51(Issue 53) pp:10620-10623
Publication Date(Web):18 May 2015
DOI:10.1039/C5CC02808F
Quasi oxygen-deficient indium tin oxide nanoparticles (ITO NPs) were prepared by photoinduced chlorine doping, and exhibited much enhanced electrocatalytic activity for oxygen reduction reaction (ORR) in alkaline media, as compared with pristine ITO.
Co-reporter:Wenhan Niu, Ligui Li, Xiaojun Liu, Weijia Zhou, Wei Li, Jia Lu, Shaowei Chen
International Journal of Hydrogen Energy 2015 Volume 40(Issue 15) pp:5106-5114
Publication Date(Web):27 April 2015
DOI:10.1016/j.ijhydene.2015.02.095
•Mixing carbon nanospheres with graphene sheets produces a sandwich GCG structure.•One-pot hydrothermal synthesis of Pt3Ni nanoparticles supported on GCG.•Enhanced electrochemical surface area by the formation of GCG sandwich structure.•Markedly improved catalytic activity of Pt3Ni-GCG in methanol oxidation.•Remarkable stability and resistance against CO poisoning of Pt3Ni-GCG.A facile method was demonstrated for the preparation of Pt3Ni alloy nanoparticles supported on a sandwich-like graphene sheets/carbon nanospheres/graphene sheets substrate (Pt3Ni–C/rGO) through a one-pot solvothermal process in N,N-dimethylformide without the addition of reducing agents and surfactants. Transmission electron microscopic measurements showed that carbon nanospheres were homogeneously dispersed in the matrix of exfoliated graphene sheets, and Pt3Ni nanoparticles were distributed on the graphene surfaces without apparent agglomeration, where the average core size was estimated to be 12.6 ± 2.4 nm. X-ray photoelectron spectroscopic studies demonstrated that electron transfer likely occurred from the Pt3Ni alloy nanoparticles to the graphene sheets. Electrochemical measurements showed that the mass activity of the Pt3Ni–C/rGO catalysts in methanol oxidation was 1.7-times higher than that of Pt3Ni nanoparticles supported on reduced graphene oxide alone (Pt3Ni/rGO), and 1.3-times higher than that of commercial Pt/C (20 wt%). Additionally, CO tolerance and durability were also remarkably enhanced. These superior electrocatalytic activities were attributed to the following major factors: (i) the insertion of carbon nanospheres into the graphene matrix prevented restacking/refolding of the graphene sheets, leading to an increasing number of accessible active sites as well as transport channels for mass and charges; and (ii) the synergetic effect between Pt3Ni nanoparticles and rGO weakened the bonding interactions with reactant species, as manifested by the enhanced kinetics of methanol oxidation and CO oxidative desorption.
Co-reporter:Xiaojun Liu;Dr. Ligui Li;Dr. Weijia Zhou;Yucheng Zhou;Wenhan Niu;Dr. Shaowei Chen
ChemElectroChem 2015 Volume 2( Issue 6) pp:803-810
Publication Date(Web):
DOI:10.1002/celc.201500002
Abstract
A synthetic method was developed for the preparation of N-doped porous carbon through hydrothermal treatment at controlled temperatures by using glucose and dicyandiamide as precursors and ZnCl2 as an activation reagent. Nitrogen doping was quantitatively determined by using XPS measurements and identified in the forms of pyridinic, pyrrolic, graphitic, and pyridinic N+O−nitrogen atoms. Further structural analysis by using SEM, TEM, XRD, Raman, FTIR, and BET measurements showed that the N-doped porous carbons exhibited a microcrystalline graphite structure and a high specific surface area up to 1000 m2 g−1. Electrochemical studies showed that the samples all exhibited a remarkable ORR catalytic activity in alkaline media, which was comparable to that of state-of-the-art Pt/C catalysts, and the one prepared at 800 °C was found to be the best among the series with an onset potential of +0.96 V, almost complete reduction of oxygen to OH−, and superior methanol tolerance and cycling stability.
Co-reporter:Xiaojun Liu;Dr. Ligui Li;Dr. Weijia Zhou;Yucheng Zhou;Wenhan Niu;Dr. Shaowei Chen
ChemElectroChem 2015 Volume 2( Issue 6) pp:
Publication Date(Web):
DOI:10.1002/celc.201590027
Co-reporter:Xiaojun Liu, Ligui Li, Meixia Ye, Yang Xue and Shaowei Chen
Nanoscale 2014 vol. 6(Issue 10) pp:5223-5229
Publication Date(Web):25 Feb 2014
DOI:10.1039/C4NR00328D
Gold nanoparticles were stabilized by a polyaniline:poly(sodium 4-styrenesulfonate) (PANI:PSS) matrix and readily dispersed in water over a wide range of pH. In contrast to nanoparticles passivated by alkanethiolates that formed a compact capping layer on the nanoparticle surface, the PANI:PSS–Au nanocomposites exhibited apparent catalytic activity in the reduction of 4-nitrophenol in the presence of excessive NaBH4, with reasonably good recyclability, which was likely due to the large accessible surface area. In addition, the PANI:PSS–Au nanocomposites also demonstrated peroxidase-like catalytic activity as evidenced by the colorimetric detection of H2O2 and glucose with PANI:PSS–Au as the enzymatic mimic. The present method may find potential applications in the design, preparation and functionalization of noble nanoparticles as efficient, versatile, and recyclable catalysts with high dispersibility and stability in aqueous media.
Co-reporter:Nan Wang, Wenhan Niu, Ligui Li, Ji Liu, Zhenghua Tang, Weijia Zhou and Shaowei Chen
Chemical Communications 2015 - vol. 51(Issue 53) pp:NaN10623-10623
Publication Date(Web):2015/05/18
DOI:10.1039/C5CC02808F
Quasi oxygen-deficient indium tin oxide nanoparticles (ITO NPs) were prepared by photoinduced chlorine doping, and exhibited much enhanced electrocatalytic activity for oxygen reduction reaction (ORR) in alkaline media, as compared with pristine ITO.
Co-reporter:Wenhan Niu, Ligui Li, Nan Wang, Shuaibo Zeng, Ji Liu, Dengke Zhao and Shaowei Chen
Journal of Materials Chemistry A 2016 - vol. 4(Issue 28) pp:NaN10827-10827
Publication Date(Web):2016/05/12
DOI:10.1039/C6TA03570A
The electrocatalytic activity of nitrogen-doped carbons towards the oxygen reduction reaction is largely determined by the concentration of active nitrogen dopants and the electrochemically accessible surface area. Herein we report a novel, facile route for the preparation of N-doped carbons based on direct pyrolysis of polypyrrole nanosheet precursors synthesized by confining the polymerization on the surface of NaCl crystals using FeCl3 as both the initiator and dopant. In the heating-up process of pyrolysis, a large amount of homogeneously distributed FeCl3 dopant and its derivatives gradually evolved into volatile nanoparticles which helped to generate abundant hierarchical macro- and meso-pores, resulting in honeycomb-like porous carbons with a high content of nitrogen dopants ranging from 7 to 18 at%, a large surface area, and an ORR activity superior to that of commercial Pt/C in alkaline electrolytes. Significantly, by using the best sample that was prepared at 800 °C (HPC-800) as the air electrode, a Zn–air battery was found to display a specific capacity of 647 mA h g−1 at 10 mA cm−2 and a negligible loss of voltage even after continuous operation for 110 h, a performance markedly better than that with Pt/C as the air cathode. The results not only highlight the significance of precursor engineering in the synthesis of highly efficient nitrogen-doped carbon catalysts for oxygen electroreduction, but also suggest the high potential of the interfacially confined polymerization method in the scalable preparation of cost-effective, highly porous carbons for electrochemical energy storage and conversion devices.
Co-reporter:Yi Peng, Bingzhang Lu, Nan Wang, Ligui Li and Shaowei Chen
Physical Chemistry Chemical Physics 2017 - vol. 19(Issue 14) pp:NaN9348-9348
Publication Date(Web):2017/01/26
DOI:10.1039/C6CP08925A
Polymer electrolyte membrane fuel cells represent a next-generation power supply technology that may be used in a diverse range of applications. Towards this end, the rational design and engineering of functional nanomaterials as low-cost, high-performance catalysts is of critical significance in the wide-spread commercialization of fuel cell technology. One major bottleneck is the oxygen reduction reaction (ORR) at the cathode. Whereas platinum-based nanoparticles have been used as the catalysts of choice, further engineering of the nanoparticles is urgently needed to enhance the catalytic performance and concurrently reduce the costs. Extensive research has also been extended to non-platinum metals or even metal-free nanocatalysts that may be viable alternatives to platinum. In this review article, we will summarize recent progress in these areas of research within the context of interfacial electron transfer: (a) interactions between metal elements in alloy nanoparticles, (b) metal–ligand interfacial bonding interactions, (c) metal–carbon substrate interactions, and (d) heteroatom doping of graphitic carbons. Results have shown that ready manipulation of the electronic interactions between the catalyst surface and oxygen species may serve as a fundamental mechanism for the optimization of the catalytic performance.
