Yi Ding - Cochemist

Atomic Observation of Catalysis-Induced Nanopore Coarsening of Nanoporous Gold

Co-reporter:Takeshi Fujita, Tomoharu Tokunaga, Ling Zhang, Dongwei Li, Luyang Chen, Shigeo Arai, Yuta Yamamoto, Akihiko Hirata, Nobuo Tanaka, Yi Ding, and Mingwei Chen

Nano Letters 2014 Volume 14(Issue 3) pp:1172-1177

Publication Date(Web):February 7, 2014

DOI:10.1021/nl403895s

Dealloyed nanoporous metals have attracted much attention because of their excellent catalytic activities toward various chemical reactions. Nevertheless, coarsening mechanisms in these catalysts have not been experimentally studied. Here, we report in situ atomic-scale observations of the structural evolution of nanoporous gold during catalytic CO oxidation. The catalysis-induced nanopore coarsening is associated with the rapid diffusion of gold atoms at chemically active surface steps and the surface segregation of residual Ag atoms, both of which are stimulated by the chemical reaction. Our observations provide the first direct evidence that planar defects hinder nanopore coarsening, suggesting a new strategy for developing structurally stable and highly active heterogeneous catalysts.

Dispersing Pt atoms onto nanoporous gold for high performance direct formic acid fuel cells

Co-reporter:Rongyue Wang, Jianguo Liu, Pan Liu, Xuanxuan Bi, Xiuling Yan, Wenxin Wang, Xingbo Ge, Mingwei Chen and Yi Ding

Chemical Science 2014 vol. 5(Issue 1) pp:403-409

Publication Date(Web):14 Oct 2013

DOI:10.1039/C3SC52792A

Direct formic acid fuel cells (DFAFCs) are promising portable energy conversion devices for supplying our off-grid energy demands. However, traditional Pt-based catalysts suffer from poor performance; consequently the precious metal loading in an actual fuel cell has to be maintained at a very high value, typically orders of magnitude higher than the acceptable level. Through a molecular self-assembly/electro-deposition process, Pt atoms are effectively dispersed onto the surface of a nanoporous gold substrate, and the resulting nanocomposites demonstrate superior electrocatalytic performance toward formic acid electro-oxidation, which can be attributed to a nearly ideal catalyst configuration where all the Pt atoms are involved in a highly desired direct reaction path. In both half-cell electrochemical testing and actual DFAFCs, these rationally designed electrodes show over two orders of magnitude improvement in Pt efficiency, as compared with the state-of-the-art Pt/C catalyst. This design strategy allows customized development of new generation electrocatalysts for high performance energy saving technologies.

3D binder-free Cu2O@Cu nanoneedle arrays for high-performance asymmetric supercapacitors

Co-reporter:Chaoqun Dong, Yan Wang, Junling Xu, Guanhua Cheng, Wanfeng Yang, Tianyi Kou, Zhonghua Zhang and Yi Ding

Journal of Materials Chemistry A 2014 vol. 2(Issue 43) pp:18229-18235

Publication Date(Web):17 Sep 2014

DOI:10.1039/C4TA04329D

Nanostructured Cu oxides/hydroxides are promising materials for supercapacitors because of their high theoretical capacitance, low cost and friendliness to environment. However, the development of commercially viable Cu oxides/hydroxides with superior capacitive performance is still challenging. Here, 3D binder-free Cu2O@Cu nanoneedle arrays electrode was developed via facile electrochemistry. The electrode exhibits a high capacitance of 862.4 F g−1 and excellent cycling stability (20000 cycles). Furthermore, we have successfully constructed a Cu2O@Cu//AC asymmetric supercapacitor, which can achieve an energy density of 35.6 W h kg−1 at 0.9 kW kg−1 and excellent stability with a capacitance retention of 92% after 10000 cycles. After being charged for dozens of seconds, the in-series Cu2O@Cu//AC supercapacitors can light up LED arrays and even charge a mobile phone. These fascinating performances reasonably indicate their potential in commercial applications for energy storage.

Nanoporous palladium catalyzed silicon-based one-pot cross-coupling reaction of aryl iodides with organosilanes

Co-reporter:Zhiwen Li, Sha Lin, Lisha Ji, Zhonghua Zhang, Xiaomei Zhang and Yi Ding

Catalysis Science & Technology 2014 vol. 4(Issue 6) pp:1734-1737

Publication Date(Web):13 Mar 2014

DOI:10.1039/C4CY00256C

One-pot cross-coupling of aryl iodides with organosilanes is realized in excellent yield by utilizing dealloyed nanoporous palladium as a sustainable and heterogeneous catalyst. The reaction is completed under mild conditions and the catalyst can be reused several times without evident loss of its catalytic activity.

Ultra-thin layer structured anodes for highly durable low-Pt direct formic acid fuel cells

Co-reporter:Rongyue Wang;Jianguo Liu;Pan Liu;Xuanxuan Bi;Xiuling Yan;Wenxin Wang

Nano Research 2014 Volume 7( Issue 11) pp:1569-1580

Publication Date(Web):2014 November

DOI:10.1007/s12274-014-0517-9

Direct formic acid fuel cells (DFAFCs) allow highly efficient low temperature conversion of chemical energy into electricity and are expected to play a vital role in our future sustainable society. However, the massive precious metal usage in current membrane electrode assembly (MEA) technology greatly inhibits their actual applications. Here we demonstrate a new type of anode constructed by confining highly active nanoengineered catalysts into an ultra-thin catalyst layer with thickness around 100 nm. Specifically, an atomic layer of platinum is first deposited onto nanoporous gold (NPG) leaf to achieve high utilization of Pt and easy accessibility of both reactants and electrons to active sites. These NPG-Pt core/shell nanostructures are further decorated by a sub-monolayer of Bi to create highly active reaction sites for formic acid electro-oxidation. Thus obtained layer-structured NPG-Pt-Bi thin films allow a dramatic decrease in Pt usage down to 3 μg·cm−2, while maintaining very high electrode activity and power performance at sufficiently low overall precious metal loading. Moreover, these electrode materials show superior durability during half-year test in actual DFAFCs, with remarkable resistance to common impurities in formic acid, which together imply their great potential in applications in actual devices.

Unsupported nanoporous gold for heterogeneous catalysis

Co-reporter:Xiaomei Zhang and Yi Ding

Catalysis Science & Technology 2013 vol. 3(Issue 11) pp:2862-2868

Publication Date(Web):13 May 2013

DOI:10.1039/C3CY00241A

Nanoporous gold fabricated by dealloying represents a new type of heterogeneous catalysts. It has attracted arising interest from the catalysis science and technology community in recent years due to its unique structural properties, including open nanoporosity, high surface area, excellent electrical conductivity, nontoxicity nature, easy recyclability, and tunable surface chemistry. This mini-review summarizes recent advances in this exciting field and emphasizes novel performance in important heterogeneous catalytic applications.

Selective Gas-Phase Oxidation of Alcohols over Nanoporous Silver

Co-reporter:Zhiwen Li;Junling Xu;Xiaohu Gu;Kang Wang;Wenhui Wang;Dr. Xiaomei Zhang;Dr. Zhonghua Zhang;Dr. Yi Ding

ChemCatChem 2013 Volume 5( Issue 7) pp:1705-1708

Publication Date(Web):

DOI:10.1002/cctc.201200862

Nanoporous surface alloys as highly active and durable oxygen reduction reaction electrocatalysts

Co-reporter:Rongyue Wang, Caixia Xu, Xuanxuan Bi and Yi Ding

Energy & Environmental Science 2012 vol. 5(Issue 1) pp:5281-5286

Publication Date(Web):27 Oct 2011

DOI:10.1039/C1EE02243A

It is of critical importance to design and fabricate highly active and durable oxygen reduction reaction (ORR) catalysts for the application of proton exchange membrane fuel cells (PEMFCs). By a simple two-step dealloying process, the active components in a Pt/Ni/Al ternary alloy were sequentially leached out in a highly controllable manner, generating a novel nanoporous surface alloy structure. Characterized by an open bicontinuous spongy morphology, the resulting nanostructure is interconnected by ∼3 nm diameter ligaments which are comprised of a Pt/Ni alloy core and a nearly pure Pt surface. In the absence of any catalyst support, these nanoporous surface alloys show much enhanced durability and electrocatalytic activity for ORR as compared to the commercial Pt/C catalyst. At a high potential, such as 0.9 V versusRHE, nanoporous Pt/Ni surface alloys show a remarkable specific activity of 1.23 mA cm−2. These nanomaterials thus hold great potential as cathode catalysts in PEMFCs in terms of facile preparation, clean catalyst surface, and enhanced ORR activity and durability.

Xylanase immobilized nanoporous gold as a highly active and stable biocatalyst

Co-reporter:Xiuling Yan, Xia Wang, Peng Zhao, Ye zhang, Ping Xu, Yi Ding

Microporous and Mesoporous Materials 2012 Volume 161() pp:1-6

Publication Date(Web):1 October 2012

DOI:10.1016/j.micromeso.2012.05.017

Dealloyed nanoporous gold, a nanostructured metallic sponge with tunable porosity and excellent biocompatibility, was employed as an effective support material for xylanase immobilization. Structure analyses revealed that the immobilization of xylanase was realized via chemical bonding of sulfur end-groups with gold surface atoms. The activity and stability for the immobilized enzyme were investigated under different conditions. And the immobilized enzymes were found to keep as high as 80% of the activity of free ones. Notably, these novel nanobiocatalysts showed quite impressive stability. Even after ten reaction cycles, this bio-nanocomposite could still retain ∼60% of the initial activity.Graphical abstractThe morphology and composition of nanoporous gold before and after immobilized xylanase are verified by SEM and EDS, which providing a primary evidence of successful enzyme immobilization on the nanobiocatalyst.Highlights► Xylanase-nanoporous gold was fabricated as an interesting type of ‘green biocatalyst’. ► It presents highly activity and stability. ► It is easy in the preparation and separation. ► It is efficient and cost-effective. ► The carrier, nanoporous gold, is a tunable porous structure to accommodate difference enzymes.

Sub-Micrometer-Thick All-Solid-State Supercapacitors with High Power and Energy Densities

Co-reporter:Fanhui Meng

Advanced Materials 2011 Volume 23( Issue 35) pp:4098-4102

Publication Date(Web):

DOI:10.1002/adma.201101678

Flexible Electronics: Sub-Micrometer-Thick All-Solid-State Supercapacitors with High Power and Energy Densities (Adv. Mater. 35/2011)

Co-reporter:Fanhui Meng

Advanced Materials 2011 Volume 23( Issue 35) pp:

Publication Date(Web):

DOI:10.1002/adma.201190138

Boosting the performance of Pt electro-catalysts toward formic acid electro-oxidation by depositing sub-monolayer Au clusters

Co-reporter:Xuanxuan Bi, Rongyue Wang, Yi Ding

Electrochimica Acta 2011 Volume 56(Issue 27) pp:10039-10043

Publication Date(Web):30 November 2011

DOI:10.1016/j.electacta.2011.08.101

CO poisoning is the main obstacle to the application of Pt nanoparticles as anode catalysts in direct formic acid fuel cells (DFAFCs). Significant types of Pt alloys have been investigated, which often demonstrate evidently improved catalytic performance governed by difference mechanisms. By using a well-known electrochemical technique of under potential deposition and in situ redox replacement, sub-monolayer Au clusters are deposited onto Pt nanoparticle surfaces in a highly controlled manner, generating a unique surface alloy structure. Under optimum conditions, the modified Pt nanoparticles can exhibit greatly enhanced specific activity (up to 23-fold increase) at potential of −0.2 V vs. MSE toward formic acid electro-oxidation (FAEO). Interestingly, the mass specific activity can also be improved by a factor of 2.3 at potential of −0.35 V vs. MSE although significant amount of surface Pt atoms are covered by the overlayer Au clusters. The much enhanced catalytic activity can be ascribed to a Pt surface ensemble effect, which induces change of the reaction path. Moreover, the sub-monolayer Au coating on the surface also contributes to the enhanced catalyst durability by inhibiting the Pt oxidation. These results show great potential to rationally design more active and stable nanocatalysts by modifying the Pt surface with otherwise inactive materials.Highlights► Au decoration on Pt nanoparticles simultaneously increases the activity and stability. ► Sub-monolayer Au decoration changes the reaction path and results in the activity improvement. ► Increasing the Au coverage will increase the specific activity. ► Proper Au coverage results in a maximum mass specific activity.

Well-defined nanoporous palladium for electrochemical reductive dechlorination

Co-reporter:Wenjing Li, Houyi Ma, Lihui Huang and Yi Ding

Physical Chemistry Chemical Physics 2011 vol. 13(Issue 13) pp:5565-5568

Publication Date(Web):21 Feb 2011

DOI:10.1039/C0CP02178D

Well-defined nanoporous palladium (np-Pd) fabricated by a modified electrochemical dealloying procedure is demonstrated to be an excellent electrocatalyst material for reductive degradation of both carbon tetrachloride and chlorobenzene.

Association of Glutathione Level and Cytotoxicity of Gold Nanoparticles in Lung Cancer Cells

Co-reporter:Yunxue Zhao ; Xiaohu Gu ; Haizhang Ma ; Xigan He ; Min Liu

The Journal of Physical Chemistry C 2011 Volume 115(Issue 26) pp:12797-12802

Publication Date(Web):June 14, 2011

DOI:10.1021/jp2025413

Gold nanoparticles (GNPs) were used to evaluate their cytotoxicity toward human lung cancer cells A549. No cell proliferation inhibition was found when the cells were treated by GNPs independently. However, when L-buthionine-sulfoximine (BSO) was used to decrease the expression of glutathione (GSH) in A549 cells, GNPs showed evident cytotoxicity to cells. Interestingly, the cytotoxicity of GNPs could be reversed after adding outside source GSH into the system. Whereas GSH plays an important role in eliminating reactive oxygen species (ROS), by monitoring the intracellular levels of ROS, GNPs were observed to generate more intracellular ROS in the presence of BSO. The cytotoxicity caused by GNPs toward lung cancer cells could therefore be partially attributed to the increase in intracellular ROS levels. These results suggest that caution should be paid in the use of GNPs for in vivo tests because GNPs can serve as therapeutic agents in their own right as well as carriers for other drugs and biomolecules.

An InSitu Dealloying and Oxidation Route to Co3O4 Nanosheets and their Ambient-Temperature CO Oxidation Activity

Co-reporter:Dr. Caixia Xu;Yunqing Liu;Ce Zhou;Lin Wang;Dr. Haoran Geng;Dr. Yi Ding

ChemCatChem 2011 Volume 3( Issue 2) pp:399-407

Publication Date(Web):

DOI:10.1002/cctc.201000275

Abstract

Co₃O₄ nanosheets are straightforwardly fabricated through an in situ dealloying and oxidation process of etching CoAl alloy in alkaline solutions. X-ray diffraction and electron spectroscopy characterizations demonstrate the formation of a Co₃O₄ nanostructure with an intricate hierarchical nanosheet morphology comprising interconnected nanoslices with the diameter as small as 6 nm. Upon calcination in O₂ atmosphere, these novel Co₃O₄ nanosheets exhibit excellent catalytic activity toward CO oxidation in normal feed gas at ambient temperature. Catalytic tests reveal the strong influence of calcination temperature on the resultant catalytic activities, whereby 300 °C is found to be preferable possibly due to an optimum balance between the surface area and the amount of active species as compared with 200 and 450 °C. Moreover, Co₃O₄ nanosheets showed good time-on-stream catalytic stability; CO conversion at T₅₀ (the temperature for 50 % CO conversion) reduced to 37 % after 20 h, and at T₁₀₀ (the temperature for full CO conversion) the conversion only decreased to about 90 % after 15 h.

Dealloying to nanoporous Au/Pt alloys and their structure sensitive electrocatalytic properties

Co-reporter:Caixia Xu, Rongyue Wang, Mingwei Chen, Yan Zhang and Yi Ding

Physical Chemistry Chemical Physics 2010 vol. 12(Issue 1) pp:239-246

Publication Date(Web):10 Nov 2009

DOI:10.1039/B917788D

A simple and general dealloying method is employed to fabricate nanoporous Au/Pt alloys with pre-determined alloy compositions. Structural characterization by electron microscopes demonstrates that selective etching of Cu from Au/Pt/Cu alloy precursors results in the formation of three-dimensional bicontinuous porous network structures with uniform pores and ligaments less than 10 nm. X-Ray photoelectron spectroscopy and X-ray diffraction demonstrate that nanoporous Au/Pt alloys have a single-phase cubic structure with relatively uniform compositions across the samples. These high surface area alloy nanostructures show much enhanced specific activity and distinct surface reactivity toward the electrooxidation of some small organic molecules, such as methanol and formic acid, as the Au content varies within the structure, thus holding great potential for use in clean energy and environmental applications.

Nanoporous PtRu Alloys for Electrocatalysis

Co-reporter:Caixia Xu, Lin Wang, Xiaolei Mu and Yi Ding

Langmuir 2010 Volume 26(Issue 10) pp:7437-7443

Publication Date(Web):January 29, 2010

DOI:10.1021/la9041474

We describe a facile route to the straightforward fabrication of nanoporous (NP) PtRu alloys with predetermined bimetallic compositions. Electron microscopy and X-ray diffraction characterizations demonstrate that selective etching of Al from ternary PtRuAl source alloys generates three-dimensional bicontinuous NP-PtRu alloy nanostructures with a single-phase face-centered-cubic crystalline structure. X-ray photoelectron spectroscopy shows a slight electronic structure modification of Pt by alloying with Ru as well as uniform surface and bulk bimetallic ratio. With characteristic structural dimensions less than 5 nm, these high surface area bimetallic nanostructures show distinct electrocatalytic performance as the Ru content varies within the structure. Among all samples, NP-Pt70Ru30 shows the highest specific activity as well as the most negative onset potential toward methanol oxidation reaction. NP-Pt50Ru50 was found to possess a similar specific activity to the commercial E-TEK Pt50Ru50/C catalyst, but its onset and peak potentials are about 70 mV more negative. CO stripping experiments demonstrate that the adsorption of CO is the weakest on NP-Pt70Ru30, and further increasing the Ru content actually shifts the CO stripping peak to a more positive potential. Thus, the overall sequence for CO-tolerance is NP-Pt70Ru30 > NP-Pt50Ru50 ≈ Pt50Ru50/C > NP-Pt30Ru70 > Pt/C.

Gas-Phase Selective Oxidation of Benzyl Alcohol to Benzaldehyde with Molecular Oxygen over Unsupported Nanoporous Gold

Co-reporter:Dongqing Han;Tingting Xu;Jixin Su Dr.;Xiaohong Xu Dr. Dr.

ChemCatChem 2010 Volume 2( Issue 4) pp:383-386

Publication Date(Web):

DOI:10.1002/cctc.201000001

Platinum-Decorated Au Porous Nanotubes as Highly Efficient Catalysts for Formic Acid Electro-Oxidation

Co-reporter:Xiaohu Gu;Xiao Cong Dr.

ChemPhysChem 2010 Volume 11( Issue 4) pp:841-846

Publication Date(Web):

DOI:10.1002/cphc.200900927

Abstract

Au porous nanotubes (PNTs) were synthesized by a templating technique that involves the chemical synthesis of Ag nanowire precursors, electroless surface modification with Au, and selective etching. A subsequent galvanic replacement reaction between [PtCl₆]²⁻ and residual Ag generates Pt-decorated Au porous nanotubes (Pt/Au PNTs), which represents a new type of self-sustained high surface area electrocatalysts with ultra-low Pt loading. Structural characterizations with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) reveal a novel nanoarchitecture with multimodal open porosity and excellent structural continuity and integrity. Cyclic voltammetry (CV) demonstrates that these Pt/Au PNTs possess very high electrocatalytic activity toward formic acid oxidation with enhanced tolerance to CO poisoning.

Dealloying to Nanoporous Silver and Its Implementation as a Template Material for Construction of Nanotubular Mesoporous Bimetallic Nanostructures

Co-reporter:Dr. Caixia Xu;Yingying Li;Fang Tian; Yi Ding

ChemPhysChem 2010 Volume 11( Issue 15) pp:3320-3328

Publication Date(Web):

DOI:10.1002/cphc.201000313

Abstract

Nanoporous silver (NPS) is fabricated by selectively dissolving Al from AgAl alloys in corrosive electrolytes at room temperature. Electron spectroscopy characterizations demonstrate that the NaOH electrolyte is beneficial to the formation of a three-dimensional bicontinuous porous nanostructure with uniform and tunable pore and ligament dimensions of a few tens of nanometers, while processing in HCl electrolyte easily lead to coarsened porous nanostructures. The high-surface-area Ag nanostructures are demonstrated as novel effective template materials to the construction of nanotubular mesoporous Pt/Ag and Pd/Ag alloy structures, which are realized via room temperature galvanic replacement reactions with H₂PtCl₆ and K₂PdCl₄ solutions by adding a high concentration of Cl⁻ ions as a coordinating agent. Electrochemical measurements indicate that the resulting hollow and porous bimetallic nanostructures show enhanced electrocatalytic activities and CO-tolerance with better durability toward methanol and formic acid oxidation due to alloying with Ag.

DFT Study on CO Oxidation Catalyzed by PtmAun (m + n = 4) Clusters: Catalytic Mechanism, Active Component, and the Configuration of Ideal Catalysts

Co-reporter:Fang Wang, Dongju Zhang and Yi Ding

The Journal of Physical Chemistry C 2010 Volume 114(Issue 33) pp:14076-14082

Publication Date(Web):August 3, 2010

DOI:10.1021/jp101470c

By performing density functional theory calculations, we show the mechanism details of CO oxidation catalyzed by several PtmAun (m + n = 4) clusters. It is found that in all situations, the reaction prefers to proceed via the single-center pathway to the two-center pathway according to a two-step mechanism: the initial activation of O2 molecule to form a peroxide-like intermediate followed by the rupture of the peroxide bond to complete the reaction. In Pt−Au bimetallic clusters, Pt sites are the catalytically active centers, whereas Au sites are “formally spectators” for CO oxidation. The calculated barriers for the reactions mediated by bimetallic clusters Pt3Au, Pt2Au2, PtAu3, are comparable with that catalyzed by monometallic Pt4 cluster, implying that the catalytic activity of Pt centers in the bimetallic clusters seems not to be dependent on its surroundings. On the basis of the present results, we propose an ideal configuration of Pt−Au bimetallic catalysts, where each active Pt atom is suitably spaced (stabilized) by Au atoms. Such catalysts are “less expensive and more efficient” compared to the corresponding pure Pt catalysts for CO oxidation at room temperature.

Porous AgCl/Ag Nanocomposites with Enhanced Visible Light Photocatalytic Properties

Co-reporter:Yingying Li and Yi Ding

The Journal of Physical Chemistry C 2010 Volume 114(Issue 7) pp:3175-3179

Publication Date(Web):February 4, 2010

DOI:10.1021/jp911678q

Porous AgCl/Ag nanocomposites were fabricated with a facile two-step route, which involves the formation of nanoporous silver (NPS) by dealloying AgAl alloys, and a subsequent surface chlorination in a mixed solution containing H2O2 and HCl. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and UV−vis spectroscopy were used to characterize the resulting samples, which revealed a porous AgCl/Ag composite nanostructure that inherited the bicontinuous spongy morphology of NPS precursors with interconnected pore channels and solid ligaments. The existence of Ag in the structure was found to contribute greatly to enhanced absorption in the visible light region. In a test system for the degradation of methylic orange (MO) dye, it was found that porous AgCl/Ag nanocomposites performed very well as efficient and stable visible light catalysts. Under nonoptimized conditions, the MO dye degradation rate can reach as high as 0.75 mg/min·gcat with 420 nm irradiation.

Nanotubular Mesoporous Bimetallic Nanostructures with Enhanced Electrocatalytic Performance

Co-reporter:Caixia Xu;Liqin Wang;Rongyue Wang;Kai Wang;Yan Zhang;Fang Tian

Advanced Materials 2009 Volume 21( Issue 21) pp:2165-2169

Publication Date(Web):

DOI:10.1002/adma.200702700

Nanotubular Mesoporous PdCu Bimetallic Electrocatalysts toward Oxygen Reduction Reaction

Co-reporter:Caixia Xu, Yan Zhang, Liqin Wang, Liqiang Xu, Xiufang Bian, Houyi Ma and Yi Ding

Chemistry of Materials 2009 Volume 21(Issue 14) pp:3110

Publication Date(Web):June 29, 2009

DOI:10.1021/cm900244g

We describe the fabrication of novel PdCu bimetallic nanocomposites with hierarchically hollow structures through a simple galvanic replacement reaction using dealloyed nanoporous copper (NPC) as both a template and reducing agent. The reaction process was monitored by UV−vis absorbance spectra and X-ray diffraction (XRD), which clearly demonstrate a structure evolution from NPC precursor to a Pd-rich PdCu alloy structure upon the completion of the reaction. Structure characterization by means of transmission electron microscope (TEM) and scanning electron microscope (SEM) indicates that the replacement reaction between NPC and [PdCl4]2− solution results in a nanotubular mesoporous structure with a nanoporous shell, which is comprised of interconnected alloy nanoparticles with size around 3 nm. The resulted PdCu nanostructure shows superior activity toward oxygen reduction reaction (ORR) with a half-wave potential at 0.840 V, which is significantly better than that of the commercial Pt/C catalyst.

Electrocatalytic oxidation of d-glucose at nanoporous Au and Au–Ag alloy electrodes in alkaline aqueous solutions

Co-reporter:Zhaona Liu, Lihui Huang, Lili Zhang, Houyi Ma, Yi Ding

Electrochimica Acta 2009 Volume 54(Issue 28) pp:7286-7293

Publication Date(Web):1 December 2009

DOI:10.1016/j.electacta.2009.07.049

Nanoporous Au–Ag alloys with different Ag content were prepared by selective dissolution of Ag from Au42Ag58 alloy samples in HNO3 solutions. With gradual dissolution of Ag component, the corroded Au–Ag alloy samples display typical bicontinuous nanoporous structures after dealloying for more than 10 min. The as-prepared nanostructured Au–Ag alloys exhibit obviously enhanced catalytic activity towards the electrooxidation of d-glucose as compared with the uncorroded Au42Ag58 alloy. It is of interest that the existence of a tiny amount of silver in the corroded Au–Ag alloys is very advantageous to enhancing their catalytic activity for the electrooxidation of glucose. The new finding was confirmed by the significant enhancement of the catalytic activity of a nanoporous gold (NPG) electrode after modification with a monolayer of Ag atoms underpotentially deposited (UPD). The nanoporous Au–Ag alloys with appropriate amount of Ag and the NPGs modified with Ag UPD monolayers are thus expected to be promising electrocatalysts for the development of glucose sensors and glucose fuel cells.

Electrochemical sensor for detection of p-nitrophenol based on nanoporous gold

Co-reporter:Zhaona Liu, Junguo Du, Cuicui Qiu, Lihui Huang, Houyi Ma, Dazhong Shen, Yi Ding

Electrochemistry Communications 2009 Volume 11(Issue 7) pp:1365-1368

Publication Date(Web):July 2009

DOI:10.1016/j.elecom.2009.05.004

Nanoporous gold (NPG) with uniform pore sizes and ligaments was prepared by a simple dealloying method. The as-prepared NPG samples were used as the working electrodes to investigate the redox behavior of p-nitrophenol (p-NP) by cyclic voltammetry (CV). Quite different from the voltammetric behavior of polycrystalline gold electrode, the CV profiles of NPG display a pair of nearly symmetric redox waves which are ascribed to the reaction of 4-(hydroxyamino)phenol/4-nitrosophenol couple. It is interesting that this pair of redox waves are hardly affected by the isomers of p-NP; and moreover, their peak areas are linear with the concentration of p-NP in the range from 0.25 to 10 mg dm−3. Because of high sensitivity and good selectivity, NPG is expected to act as a promising electrochemical sensor material for detecting trace p-NP in wastewaters.

Au-Ag alloy nanoporous nanotubes

Co-reporter:Xiaohu Gu;Liqiang Xu;Fang Tian

Nano Research 2009 Volume 2( Issue 5) pp:386-393

Publication Date(Web):2009 May

DOI:10.1007/s12274-009-9038-3

Metallic nanostructures with hollow interiors or tailored porosity represent a special class of attractive materials with intriguing chemicophysical properties. This paper presents the fabrication of a new type of metallic nanoporous nanotube structure based on a facile and effective combination of nanocrystal growth and surface modification. By controlling the individual steps involved in this process, such as nanowire growth, surface modification, thermal diffusion, and dealloying, one-dimensional (1-D) metallic nanostructures can be prepared with tailored structural features and pre-designed functionalities. These tubular and porous nanostructures show distinct optical properties, such as tunable absorption in the near-infrared region, and enhanced capability for electrochemiluminescence signal amplification, which make them particularly desirable as novel 1-D nanocarriers for biomedical, drug delivery and sensing applications.

Enhanced Photoelectrocatalytic Activity of Methanol Oxidation on TiO2-Decorated Nanoporous Gold

Co-reporter:Chuancheng Jia, Huiming Yin, Houyi Ma, Rongyue Wang, Xingbo Ge, Aiqiu Zhou, Xiaohong Xu and Yi Ding

The Journal of Physical Chemistry C 2009 Volume 113(Issue 36) pp:16138-16143

Publication Date(Web):August 18, 2009

DOI:10.1021/jp904191k

Au−TiO2 nanocomposites have been widely investigated for their potential applications in solar energy conversion, CO oxidation, and methanol reforming reactions. In this study, commercial TiO2 nanoparticles were assembled on the surface of nanoporous gold (NPG) to fabricate novel TiO2/NPG nanocomposite electrodes. Electrochemical and photoelectrochemical techniques were used to investigate the characteristics of the electrodes. Large photocurrent and nearly reversible voltammetric responses were observed for methanol photoelectrocatalysis under UV radiation, indicating an effective elimination of gold surface passivation due to a pronounced synergistic effect between TiO2 and NPG. A possible mechanism was proposed to elucidate such a synergistic effect, which is based on the reaction of the photogenerated reactive intermediates on the surface of NPG. Kinetic studies showed that the coupling of TiO2 with NPG in our system could lead to about a 30% decrease of apparent activation energy for methanol electrooxidation.

Theoretical Study of the CO Oxidation Mediated by Au3+, Au3, and Au3−: Mechanism and Charge State Effect of Gold on Its Catalytic Activity

Co-reporter:Fang Wang, Dongju Zhang, Xiaohong Xu and Yi Ding

The Journal of Physical Chemistry C 2009 Volume 113(Issue 42) pp:18032-18039

Publication Date(Web):September 24, 2009

DOI:10.1021/jp903392w

By carrying out density functional theory calculations, we studied the CO oxidation promoted by cationic, neutral, and anionic Au trimers, which represent the prototypes of Au-cluster-based catalysts with different charge states. The reaction is explored along three possible pathways: one involves the reaction of the initial complexes between Au trimers and O2 with CO; another is related to O2 interacting with the complexes between Au trimers and CO; and the third refers to a self-promoting mechanism; that is, the second CO oxidation is promoted by a preadsorbed CO molecule. The theoretical results show that all three species may promote the reaction, as indicated by calculated low energy barriers and high exothermicities, supporting the fact that cationic, neutral, and anionic Au species were all observed to present catalytic activity toward CO oxidation. Along the reaction coordinates for all of the reactions, Au−carbonate species are not found to be the necessary intermediates, although they are calculated to be energetically very stable. In contrast, by performing atom-centered density matrix propagation molecular dynamics simulations, the formation of such highly stable species is attributed to the effective collision between Au−oxides and CO2 with the carbon atom of CO2 directly attacking the O atom in the oxides. The present results enrich our understanding of the catalytic oxidation of CO by Au-cluster-based catalysts.

Tailoring the Structure and Property of Pt-Decorated Nanoporous Gold by Thermal Annealing

Co-reporter:Xingbo Ge, Xiuling Yan, Rongyue Wang, Fang Tian and Yi Ding

The Journal of Physical Chemistry C 2009 Volume 113(Issue 17) pp:7379-7384

Publication Date(Web):2017-2-22

DOI:10.1021/jp9008702

We study the structure evolution of a novel electrocatalyst, Pt-decorated nanoporous gold (Pt-NPG), during thermal annealing at relatively low temperatures. Pt-NPG was made by plating a thin layer of Pt over NPG substrate during an electroless plating process that generated epitaxial Pt nanoislands loaded on the NPG surface. In comparison with Pt’s very high melting point, thermal annealing at temperatures as low as 100 °C was found to significantly change the structure and surface chemistry of these nanomaterials. Scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and electrochemical techniques were combined to characterize the structures of Pt-NPG annealed under various conditions. While Pt-NPG preserved very well its initial porous morphology, the deposited Pt islands collapsed to form a thin Au−Pt alloy layer coating on the NPG surface upon heating. This structure change results in severe modulation to the electronic structure and surface reactivity of Pt, which were proved by markedly different behaviors in electrocatalytic reactions such as formic acid electro-oxidation and CO stripping. These findings provide considerable insight into the Au−Pt bimetallic system and pave the way for the application of Pt-NPG in fuel cell technologies.

Immobilization of Lipases onto Magnetic Fe3O4 Nanoparticles for Application in Biodiesel Production

Co-reporter:Xia Wang Dr.;Peipei Dou;Peng Zhao;Chuanming Zhao ;Ping Xu

ChemSusChem 2009 Volume 2( Issue 10) pp:947-950

Publication Date(Web):

DOI:10.1002/cssc.200900174

Facile Fabrication of Ultrathin Pt Overlayers onto Nanoporous Metal Membranes via Repeated Cu UPD and in Situ Redox Replacement Reaction

Co-reporter:Pengpeng Liu, Xingbo Ge, Rongyue Wang, Houyi Ma and Yi Ding

Langmuir 2009 Volume 25(Issue 1) pp:561-567

Publication Date(Web):December 8, 2008

DOI:10.1021/la8027034

Ultrathin Pt films from one to several atomic layers are successfully decorated onto nanoporous gold (NPG) membranes by utilizing under potential deposition (UPD) of Cu onto Au or Pt surfaces, followed by in situ redox replacement reaction (RRR) of UPD Cu by Pt. The thickness of Pt layers can be controlled precisely by repeating the Cu−UPD−RRR cycles. TEM observations coupled with electrochemical testing suggest that the morphology of Pt overlayers changes from an ultrathin epitaxial film in the case of one or two atomic layers to well-dispersed nanoislands in the case of four and more atomic layers. Electron diffraction (ED) patterns confirm that the as-prepared NPG−Pt membranes maintain a single-crystalline structure, even though the thickness of Pt films reaches six atomic layers, indicating the decorated Pt films hold the same crystallographic relationship to the NPG substrate during the entire fabrication process. Due to the regular modulation of Pt utilization, the electrocatalytic activity of NPG−Pt exhibits interesting surface structure dependence in methanol, ethanol, and CO electrooxidation reactions. These novel bimetallic nanocatalysts show excellent electrocatalytic activity and much enhanced poison tolerance as compared to the commercial Pt/C catalysts. The success in the fabrication of NPG−Pt-type materials provides a new path to prepare electrocatalysts with ultralow Pt loading and high Pt utilization, which is of great significance in energy-related applications, such as direct alcohol fuel cells (DAFCs).

Structure dependent electrooxidation of small organic molecules on Pt-decorated nanoporous gold membrane catalysts

Co-reporter:Xingbo Ge, Rongyue Wang, Songzhi Cui, Fang Tian, Liqiang Xu, Yi Ding

Electrochemistry Communications 2008 Volume 10(Issue 10) pp:1494-1497

Publication Date(Web):October 2008

DOI:10.1016/j.elecom.2008.07.045

We describe the electrocatalytic properties of self-supported Pt-decorated nanoporous gold (Pt-NPG) membranes towards the electrooxidation of formic acid and some other small organic molecules. By effectively enhancing the Pt utilization and providing a unique surface structure, the electrooxidation of formic acid on Pt-NPG was found to be highly sensitive to its surface structure. An unparalleled increase by nearly two orders of magnitude in catalytic activity was achieved on NPG electrodes decorated with sub-monolayer Pt atoms, as compared to the commercial Pt/C catalyst under the same testing conditions.

Electrocatalytic activity of bimetallic platinum–gold catalysts fabricated based on nanoporous gold

Co-reporter:Jintao Zhang, Houyi Ma, Dongju Zhang, Pengpeng Liu, Fang Tian and Yi Ding

Physical Chemistry Chemical Physics 2008 vol. 10(Issue 22) pp:3250-3255

Publication Date(Web):17 Apr 2008

DOI:10.1039/B718192B

A tiny amount of Pt was deposited in a quasi-two-dimensional form onto the nanoporous gold (NPG) substrate through a simple immersion–electrodeposition (IE) method, forming nanostructured bimetallic Pt–Au catalysts. Such Pt–Au nanostructures have much higher structural stability than the bare NPG; moreover, they exhibit better catalytic activity and stronger poison resistance than commercial Pt–Ru catalysts because of the synergistic effect of the bimetallic compositions.

Aerobic Oxidation of d-Glucose on Support-Free Nanoporous Gold

Co-reporter:Huiming Yin ; Cunqi Zhou ; Caixia Xu ; Pengpeng Liu ; Xiaohong Xu

The Journal of Physical Chemistry C 2008 Volume 112(Issue 26) pp:9673-9678

Publication Date(Web):June 10, 2008

DOI:10.1021/jp8019864

Nanoporous gold (NPG) catalysts, made by dealloying Ag/Au alloys, were found to be novel unsupported Au nanocatalysts that exhibited effective catalytic activity and high selectivity (∼99%) for the aerobic oxidation of d-glucose to d-gluconic acid under mild conditions. Systematic studies have been carried out to discuss this new catalytic system, including the activity dependence as functions of pH value, temperature and NPG ligament size, reaction active sites, and reaction kinetics. The possible contribution from the residual Ag atoms trapped in the NPG ligaments was also discussed, which turned out to be unfavorable for the glucose oxidation. The unexpected observation of the catalytic activity from NPG with a ligament size as large as 60 nm indicated that the low-coordinated surface Au atoms should be the reaction active sites for glucose oxidation.

Platinum-Decorated Nanoporous Gold Leaf for Methanol Electrooxidation

Co-reporter:Xingbo Ge, Rongyue Wang, Pengpeng Liu and Yi Ding

Chemistry of Materials 2007 Volume 19(Issue 24) pp:5827

Publication Date(Web):October 24, 2007

DOI:10.1021/cm702335f

Research on unsupported nanoporous gold catalyst for CO oxidation

Co-reporter:Caixia Xu, Xiaohong Xu, Jixin Su, Yi Ding

Journal of Catalysis (10 December 2007) Volume 252(Issue 2) pp:243-248

Publication Date(Web):10 December 2007

DOI:10.1016/j.jcat.2007.09.016

Nanoporous gold (NPG), a novel unsupported gold catalyst prepared by dealloying, exhibits exceptional catalytic activity for CO oxidation. Systematic studies were carried out on this new catalytic system, including the active sites of catalysts, the reaction kinetics, and activity dependence as functions of space velocity and temperature. Our results show strong evidence that metallic gold atoms on NPG are the intrinsic active sites at which the reaction of CO with O2 occurs. The kinetic study found that the reaction rate of CO oxidation on unsupported NPG depends significantly on CO concentration but only slightly on O2 concentration. We suggest that CO adsorption plays a decisive role in CO oxidation on NPG as the rate-limiting step. By completely ruling out the support influence, our findings provide considerable insight into the role of gold catalysts.

Dispersing Pt atoms onto nanoporous gold for high performance direct formic acid fuel cells

Co-reporter:Rongyue Wang, Jianguo Liu, Pan Liu, Xuanxuan Bi, Xiuling Yan, Wenxin Wang, Xingbo Ge, Mingwei Chen and Yi Ding

Chemical Science (2010-Present) 2014 - vol. 5(Issue 1) pp:NaN409-409

Publication Date(Web):2013/10/14

DOI:10.1039/C3SC52792A

Direct formic acid fuel cells (DFAFCs) are promising portable energy conversion devices for supplying our off-grid energy demands. However, traditional Pt-based catalysts suffer from poor performance; consequently the precious metal loading in an actual fuel cell has to be maintained at a very high value, typically orders of magnitude higher than the acceptable level. Through a molecular self-assembly/electro-deposition process, Pt atoms are effectively dispersed onto the surface of a nanoporous gold substrate, and the resulting nanocomposites demonstrate superior electrocatalytic performance toward formic acid electro-oxidation, which can be attributed to a nearly ideal catalyst configuration where all the Pt atoms are involved in a highly desired direct reaction path. In both half-cell electrochemical testing and actual DFAFCs, these rationally designed electrodes show over two orders of magnitude improvement in Pt efficiency, as compared with the state-of-the-art Pt/C catalyst. This design strategy allows customized development of new generation electrocatalysts for high performance energy saving technologies.

3D binder-free Cu2O@Cu nanoneedle arrays for high-performance asymmetric supercapacitors

Co-reporter:Chaoqun Dong, Yan Wang, Junling Xu, Guanhua Cheng, Wanfeng Yang, Tianyi Kou, Zhonghua Zhang and Yi Ding

Journal of Materials Chemistry A 2014 - vol. 2(Issue 43) pp:NaN18235-18235

Publication Date(Web):2014/09/17

DOI:10.1039/C4TA04329D

Nanostructured Cu oxides/hydroxides are promising materials for supercapacitors because of their high theoretical capacitance, low cost and friendliness to environment. However, the development of commercially viable Cu oxides/hydroxides with superior capacitive performance is still challenging. Here, 3D binder-free Cu2O@Cu nanoneedle arrays electrode was developed via facile electrochemistry. The electrode exhibits a high capacitance of 862.4 F g−1 and excellent cycling stability (20000 cycles). Furthermore, we have successfully constructed a Cu2O@Cu//AC asymmetric supercapacitor, which can achieve an energy density of 35.6 W h kg−1 at 0.9 kW kg−1 and excellent stability with a capacitance retention of 92% after 10000 cycles. After being charged for dozens of seconds, the in-series Cu2O@Cu//AC supercapacitors can light up LED arrays and even charge a mobile phone. These fascinating performances reasonably indicate their potential in commercial applications for energy storage.

Well-defined nanoporous palladium for electrochemical reductive dechlorination

Co-reporter:Wenjing Li, Houyi Ma, Lihui Huang and Yi Ding

Physical Chemistry Chemical Physics 2011 - vol. 13(Issue 13) pp:NaN5568-5568

Publication Date(Web):2011/02/21

DOI:10.1039/C0CP02178D

Well-defined nanoporous palladium (np-Pd) fabricated by a modified electrochemical dealloying procedure is demonstrated to be an excellent electrocatalyst material for reductive degradation of both carbon tetrachloride and chlorobenzene.

Electrocatalytic activity of bimetallic platinum–gold catalysts fabricated based on nanoporous gold

Co-reporter:Jintao Zhang, Houyi Ma, Dongju Zhang, Pengpeng Liu, Fang Tian and Yi Ding

Physical Chemistry Chemical Physics 2008 - vol. 10(Issue 22) pp:NaN3255-3255

Publication Date(Web):2008/04/17

DOI:10.1039/B718192B

A tiny amount of Pt was deposited in a quasi-two-dimensional form onto the nanoporous gold (NPG) substrate through a simple immersion–electrodeposition (IE) method, forming nanostructured bimetallic Pt–Au catalysts. Such Pt–Au nanostructures have much higher structural stability than the bare NPG; moreover, they exhibit better catalytic activity and stronger poison resistance than commercial Pt–Ru catalysts because of the synergistic effect of the bimetallic compositions.

Dealloying to nanoporous Au/Pt alloys and their structure sensitive electrocatalytic properties

Co-reporter:Caixia Xu, Rongyue Wang, Mingwei Chen, Yan Zhang and Yi Ding

Physical Chemistry Chemical Physics 2010 - vol. 12(Issue 1) pp:NaN246-246

Publication Date(Web):2009/11/10

DOI:10.1039/B917788D

A simple and general dealloying method is employed to fabricate nanoporous Au/Pt alloys with pre-determined alloy compositions. Structural characterization by electron microscopes demonstrates that selective etching of Cu from Au/Pt/Cu alloy precursors results in the formation of three-dimensional bicontinuous porous network structures with uniform pores and ligaments less than 10 nm. X-Ray photoelectron spectroscopy and X-ray diffraction demonstrate that nanoporous Au/Pt alloys have a single-phase cubic structure with relatively uniform compositions across the samples. These high surface area alloy nanostructures show much enhanced specific activity and distinct surface reactivity toward the electrooxidation of some small organic molecules, such as methanol and formic acid, as the Au content varies within the structure, thus holding great potential for use in clean energy and environmental applications.

Unsupported nanoporous gold for heterogeneous catalysis

Co-reporter:Xiaomei Zhang and Yi Ding

Catalysis Science & Technology (2011-Present) 2013 - vol. 3(Issue 11) pp:NaN2868-2868

Publication Date(Web):2013/05/13

DOI:10.1039/C3CY00241A

Nanoporous gold fabricated by dealloying represents a new type of heterogeneous catalysts. It has attracted arising interest from the catalysis science and technology community in recent years due to its unique structural properties, including open nanoporosity, high surface area, excellent electrical conductivity, nontoxicity nature, easy recyclability, and tunable surface chemistry. This mini-review summarizes recent advances in this exciting field and emphasizes novel performance in important heterogeneous catalytic applications.

Nanoporous palladium catalyzed silicon-based one-pot cross-coupling reaction of aryl iodides with organosilanes

Co-reporter:Zhiwen Li, Sha Lin, Lisha Ji, Zhonghua Zhang, Xiaomei Zhang and Yi Ding

Catalysis Science & Technology (2011-Present) 2014 - vol. 4(Issue 6) pp:NaN1737-1737

Publication Date(Web):2014/03/13

DOI:10.1039/C4CY00256C

One-pot cross-coupling of aryl iodides with organosilanes is realized in excellent yield by utilizing dealloyed nanoporous palladium as a sustainable and heterogeneous catalyst. The reaction is completed under mild conditions and the catalyst can be reused several times without evident loss of its catalytic activity.