Study On The Performance Of High Porosity Nanoporous Gold Supported Platinum In Acidic And Alkaline Exchange Membrane Fuel Cells

In order to solve the environmental pollution caused by the ever-increasing global energy consumption and the use of fossil fuel energy,the world is in the process of the third energy transition,and global renewable and environmentally friendly energy has become an important direction of the transition.In recent years,low-temperature fuel cells have been widely concerned and developed under the guidance of policies.The membrane electrode assemblies（MEAs）,which are the core parts of fuel cells,are the place where many substances transfer and electrochemical reactions occur,involving three-phase interfacial reactions and complex mass and heat transfer processes.The most widely used commercial electrode is the frame structure of solid network composed of platinum-based catalyst,carbon powder and ionomer mixed spraying,which transmits protons,electrons,gas reactants and liquid products,respectively.However,such structure leads to the mutual restriction between charge transfer and material transport capacity,and cannot give full play to the theoretical activity of electrode catalyst itself.In this paper,nanoporous gold supported platinum based alloy thin film materials were prepared by dealloying method.On the basis of this material,nanoporous structure ultrathin film electrodes were constructed.The concept of ultrathin three-dimensional（3D）nanoporous metal ordered film MEAs was used to meet the requirements of low Pt loading,good battery performance and durability of catalysts.The porosity of the membrane electrode catalyst layer is one of the important parameters that affect the performance and stability of the proton exchange membrane fuel cell.The catalyst layer has sufficient void volume to allow the three-phase boundary construction of the electrode part of the fuel cell membrane to promote the material transmission in the electrode and appropriate water management.The specific research content is as follows:1.The porosity in the porous electrode is related to mass transfer.The zigzag nano-structure channel in the porous electrode is the fundamental reason for the increase of the macroscopic mass transfer resistance,which will hinder the material transfer in the membrane electrode assemblies（MEAs）.Therefore,for the ultra-thin3D catalytic layer structure,it is necessary to maintain a high porosity for maintaining the performance and durability of the fuel cell.Therefore,the first part of this paper focuses on the preparation of nanoporous ultrathin catalysts with different porosities and the performance test in RDE environment and single fuel cell environment through theoretical simulation method.The porosity of nanoporous gold（NPG）was increased by controlling the atomic ratio of precursor and corrosion conditions,and the ligament size of the two porosity materials was maintained.The effect of porosity on the performance of proton exchange membrane fuel cell（PEMFC）was studied by simulation.The results show that when the catalyst layer porosity is less than 50%,the fuel cell performance increases with the increase of porosity.Then,the performance of NPG-Pt catalysts with different porosity in RDE environment and single fuel cell was tested.The results showed that the nanoporous metal electrode with high porosity had higher battery performance.The optimized nanoporous metal（NPM）showed excellent performance for PEMFC,and its power density was 1.2times that of commercial MEA.NPM also showed high stability within 2.3 h,exceeding most Pt-based PEMFC catalysts.2.Porosity and pore structure have a crucial influence on the catalytic layer of AEMFC.Studies have shown that the surface defect position of the catalyst is the catalytic activity center,and the Pt site with highly coordinated number（HCN）catalytic activity is conducive to improving the catalytic activities of hydrogen oxidation reaction（HOR）and oxygen reduction reaction（ORR）.Compared with traditional nanoparticle catalysts,NPG has a higher proportion of HCN Au atoms,the number of HCN atoms increases with decreasing pore size and ligament size of NPG.The platinum-supported nanoporous gold（NPG-Pt）catalyst forms a core-shell structure by epitaxially growing Pt on the surface of the NPG,and can also continue the surface structure of the NPG to form HCN Pt atoms,thereby improving the reaction activity of the catalyst.The results showed that the mass activities of the best NPG-Pt catalysts HOR and ORR were 3.53 and 3.70 times higher than those of commercial Pt/C catalysts,the exchange current density of NPG_{15 nm}-Pt catalyst in HOR was 1.80 times higher than that of commercial Pt/C at 0.05 V,and the specific activity of NPG_{15 nm}-Pt catalyst in ORR was 3.91 times higher than that of commercial Pt/C catalyst.