Preparation Of Nanoporous Pt-based Materials And Their Methanol Electrooxidation Activities

This paper is focusing on the design and fabrication of nanoporous platinum-based materials, and exploring their catalytic properties towards methanol electroxidation. Investigations are based on several aspects mainly including:the preparation of unsupported nanoporous, and nanoporous PtCo and PtNi alloys by using room-temperature dealloying method. This paper aims to develop a simple and effective way to prepare the Pt-based catalyst materials, and explore their application potentials in direct methanol fuel cells.1. Preparation of nanoporous platinum and its electro-catalytic properties towards methanolNanoporous platinum was fabricated by a simple dealloying method. Electron microscope characterizations show that selectively etching Al from PtAl alloy precursors in alkali or acid solution can both easily prepare three-dimensional bicontinuous network nanostructures of Pt. The resulted nanostructure exhibited much enhanced catalytic performance towards methanol electrooxidation compared with commercial Pt/C catalyst. More importantly, CO stripping and potentiostatic tests demonstrated that nanoporous Pt has much higher long-term catalytic stability and CO resistance than the Pt/C catalyst.2. Alloying to preparation of Porous PtCo PtNi alloy thin and study about its methanol electrochemical oxidationNanoporous (NP) PtCo and PtNi alloy ribbons with predetermined bimetallic compositions are easily fabricated by one step of mild dealloying. Electron microscopy and X-ray diffraction confirmed that single-phase PtCo(Ni) alloy ribbons were successfully prepared by selective etching of PtCo(Ni)Al source alloy, characterized by uniform three-dimensional bicontinuous network architecture with the ligament size as small as3nm. Compared with E-TEK Pt/C catalyst, the as-made NP-PtCo(Ni) alloys exhibit superior specific activity with the lower peak potential and enhanced CO-tolerance towards methanol electrooxidation. More importantly, these nanomaterials also show much higher structure stability despite the incorporation of more reactive Co or Ni with little loss of the electrochemical surface area of Pt upon5000potential cycles in acid solution. X-ray photoelectron spectroscopy and DFT calculations revealed that alloying with Co or Ni modifies the electronic structure of Pt with the downshift of Pt d band center, resulting in the improved methanol oxidation activity and decreased CO poisoning.3. Hierarchical nanoporous PtFe alloy with multimodal size distributions and its catalytic performance towards methanol electrooxidationHierarchical nanoporous (NP) PtFe alloy with multimodal size distributions is straightforwardly fabricated by means of mild dealloying of PtFeAl source alloy. This interesting nanoporous structure consists of interconnected larger ligaments around hundreds of nanometers, in which these ligaments are also composed of the three-dimensional network structure with the typical size at3nm. By comparison with NP-Pt and Pt/C catalysts, the as-made alloy nanostructure exhibits superior electrocatalytic activity for methanol oxidation reaction (MOR) with higher catalytic durability and CO-tolerance besides the enhanced specific and mass activity. NP-PtFe also shows improved structure stability with the less loss of the electrochemical surface area of Pt upon long-term potential scan in acidic solution. The as-made hierarchical nanoporous PtFe alloy holds great potential as promising anode catalyst for direct methanol fuel cells in terms of unique catalytic performance and simple preparation.