Nanostructured Platinum & Platinum based anode electrocatalysts for direct methanol fuel cells

Ph.DDOCTOR OF PHILOSOPH

De-alloyed PtCu/C catalysts with enhanced electrocatalytic performance for the oxygen reduction reaction

After electrochemical de-alloying, PtCu/C catalyst with a rich Pt shell demonstrated an enhanced ORR activity and superior durability.National Key Research and Development Program of China (No. 2018YFB0105500

Preparation and characterization of bimetallic Pt^Ni-P/CNT catalysts via galvanic displacement reaction on electrolessly-plated Ni-P/CNT

Platinum-based bimetallic catalysts have broad applications in polymer electrolyte membrane fuel cells and water splitting. In this work, galvanic displacement reaction was employed to prepare Pt^Ni-P/CNT catalysts using electrolessly-plated Ni-P/CNT. These catalysts were extensively characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Catalytic activities towards methanol oxidation and hydrogen evolution reactions were evaluated and benchmarked with a commercial Pt/C catalyst. Uniform dispersion of Pt on Ni-P particles led to high Pt utilization, and the electrochemical surface area of Pt^Ni-P/CNT with 12.1% Pt loading was found to be 126 m2 g−1, higher than that of a commercial Pt/C (77.9 m2 g−1). The Tafel slopes for the Pt^Ni-P/CNT catalysts were also found to be smaller than that of Pt/C indicating faster kinetics for hydrogen evolution reaction. Keywords: Catalysts, Pt^Ni-P/CNT, Methanol oxidation, Electroless plating, Hydrogen evolution reactio

Methanol oxidation activities of Pt nanoparticles supported on microporous carbon with and without a graphitic shell

Platinum nanoparticles were prepared as catalysts supported on microporous amorphous carbon with and without a graphitic carbon shell. The electro-oxidation of methanol in acidic solutions at room temperature was used as a probe reaction to explore the effect of the carbon structure on catalysis. CO anodic stripping voltammetry and cyclic voltammetry both recorded enhanced performance for the catalyst supported on the carbon with a graphitic shell. Some rationalizations of the possible roles of the graphitic shell are provided

Template synthesis of microporous carbon for direct methanol fuel cell application

Ordered microporous carbon with a structure of amorphous carbon core and graphitic carbon shell was prepared using hydrogen-form zeolite Y as the template. Impregnation and chemical vapor deposition methods were employed to infiltrate carbon in the pores of the template. Physical adsorption of nitrogen, X-ray diffraction, thermogravimetric analysis, field-emission scanning electron microscope, and field-emission transmission electron microscope techniques were employed to study the structural and morphological properties of the samples. The electrochemical properties of Pt supported on the carbon samples were examined and compared with a commercial catalyst. It was observed that Pt catalyst supported on a carbon with a core/shell structure has a higher specific activity for room-temperature methanol oxidation than the commercial catalyst

Synthesis of graphitic ordered macroporous carbon with a three-dimensional interconnected pore structure for electrochemical applications

In this study, ordered macroporous carbon with a three-dimensional (3D) interconnected pore structure and a graphitic pore wall was prepared by chemical vapor deposition (CVD) of benzene using inverse silica opal as the template. Field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectrometry, nitrogen adsorption, and thermogravimetric analysis techniques were used to characterize the carbon samples. The electrochemical properties of the carbon materials as a carbon-based anode for lithium-ion batteries and as a Pt catalyst support for room-temperature methanol electrochemical oxidation were examined. It was observed that the CVD method is a simple route to fabrication of desired carbon nanostructures, affording a carbon with graphitic pore walls and uniform pores. The graphitic nature of the carbon enhances the rate performance and cyclability in lithium-ion batteries. The specific capacity was found to be further improved when SnO nanoparticles were supported on the carbon. The specific activity of Pt catalyst supported on the carbon materials for room-temperature methanol electrochemical oxidation was observed to be higher than that of a commercial Pt catalyst (E-TEK)

Uniformly dispersed carbon-supported bimetallic ruthenium-platinum electrocatalysts for the methanol oxidation reaction

Reducing the Pt-based electrocatalysts to sub-nanometer sizes is an effective way to achieve high utilization of noble metals. Herein, we report a successive route to synthesize carbon-supported bimetallic ruthenium-platinum electrocatalysts (Ru-Pt/C) with uniform dispersion and fine sizes. In this strategy, carbon-supported Ru nanoparticles (Ru/C) with a mean size of 1.4 nm are firstly prepared in a mixture of ethylene glycol and water, and the Pt precursors are then reduced in the presence of pre-formed Ru/C. The average diameter of the bimetallic Ru-Pt particles on carbon supports is 1.9 nm, which corresponds to one to two Pt layers deposited on the surface of Ru seeds. The as-prepared bimetallic Ru-Pt/C electrocatalysts are analyzed by the CO stripping voltammetry, a diagnostic electrochemical tool. Compared with the commercial PtRu/C catalyst and the control PtRu/C prepared by a conventional co-reduction method, the bimetallic Ru-Pt/C has higher electrochemical surface area (92.5 m(2) g(-1)) and mass activity (483 A g(-1)) for methanol oxidation reaction. The strategy reported in this study is effective to produce fine bimetallic Ru-Pt particles (less than 2.0 nm) with uniform dispersion and high activity.</p

RSC Adv.

Mastery over the structure and/or composition of metal nanoparticles is an effective way to improve their catalytic activity on a mass basis. Herein, we report a facile solution route for the assembly of hollow Pt nanospheres (hPt) and ultrafine Ru nanoparticles based on electrostatic interactions. In this approach, negatively charged hollow Pt nanospheres with an average size of 12 nm and positively charged ultrafine Ru nanoparticles with an average size of 0.9 nm are first prepared, followed by the successful fabrication of hPt-Ru assemblies upon mixing the particles with opposite charges. The hPt-Ru assemblies at a Pt/Ru molar ratio of 2 : 1 exhibit superior catalytic activity toward methanol oxidation in direct methanol fuel cells for the presence of a mixed-phase containing Pt and an effective oxophilic metal, and a smaller dilution effect on the Pt surface induced by Ru in the assemblies. This study offers a vivid example to demonstrate the integration of a second oxophilic metal into the active Pt catalyst capable of enhancing its catalytic properties by means of a physical construction.Mastery over the structure and/or composition of metal nanoparticles is an effective way to improve their catalytic activity on a mass basis. Herein, we report a facile solution route for the assembly of hollow Pt nanospheres (hPt) and ultrafine Ru nanoparticles based on electrostatic interactions. In this approach, negatively charged hollow Pt nanospheres with an average size of 12 nm and positively charged ultrafine Ru nanoparticles with an average size of 0.9 nm are first prepared, followed by the successful fabrication of hPt-Ru assemblies upon mixing the particles with opposite charges. The hPt-Ru assemblies at a Pt/Ru molar ratio of 2 : 1 exhibit superior catalytic activity toward methanol oxidation in direct methanol fuel cells for the presence of a mixed-phase containing Pt and an effective oxophilic metal, and a smaller dilution effect on the Pt surface induced by Ru in the assemblies. This study offers a vivid example to demonstrate the integration of a second oxophilic metal into the active Pt catalyst capable of enhancing its catalytic properties by means of a physical construction

Pt nanoparticles supported on mesoporous carbon nanocomposites incorporated with Ni or Co nanoparticles for fuel cells

We report the preparation and characterization of mesoporous carbon nanocomposites with Ni and Co nanoparticles incorporated into the pore walls, which are synthesized via template strategy by sucrose-impregnation and benzene chemical vapor deposition (CVD) routes separately. Pt nanoparticles supported on the nanocomposites for oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) in fuel cells are fabricated via hydrogen reduction method. It is found that the introduction of metal nanoparticles into the pore walls of carbon materials via both synthesis routes had negligible change in pore structure. Highly dispersed Pt nanoparticles supported on nanocomposites synthesized by sucrose-impregnation method shows better catalytic activities for both ORR and MOR than that on those by CVD method and greatly improve the limiting current densities for ORR. The promotional effect of Ni on the catalytic activity of Pt catalysts for both ORR and MOR is evidenced in nanocomposites obtained with sucrose-impregnation method, but not with CVD method. Interesting results revealed that Ni performed as a better promoter in MOR while Co is a better promoter in ORR. Our investigation not only provides further insight on the roles of Ni and Co in ORR and MOR, but also can assist the design and synthesis of the new nanostructured electrocatalyst supports. (C) 2012 Elsevier B.V. All rights reserved

Fabrication of CdTe QDs/BiOI-Promoted TiO2 Hollow Microspheres with Superior Photocatalytic Performance Under Simulated Sunlight

Abstract Hollow and heterostructured architectures are recognized as an effective approach to improve photocatalytic performance. In this work, ternary TiO2/CdTe/BiOI with hollow structure was constructed via a step-by-step method. In addition, the effect of TiO2 structural regulation and the energy band alignment of BiOI and CdTe quantum dots (CdTe QDs) with TiO2 in TiO2/CdTe/BiOI on photocatalytic dye removal were also studied. The results reveal that the TiO2/CdTe/BiOI heterostructures with hollow substrates exhibit much higher photocatalytic activities than pure TiO2, P25, TiO2/CdTe, and TiO2/BiOI and ternary TiO2/CdTe/BiOI with solid substrates. For TiO2(H)/CdTe/BiOI, several synergistic factors may be responsible for the remarkable visible-light photodegradation performance, such as strong visible-light absorption by BiOI and larger specific surface area