Preparation Of Nanoporous Nobel Metals And Their Catalytic Performance Towards Oxygen Reduction Reaction

Proton exchange membrane fuel cells （PEMFCs） have attracted considerable researchinterests due to their great application potential as alternative energy sources in the fields ofautomotive systems and portable electronics. For PEMFCs oxygen reduction reaction （ORR）occurred at the cathode is significant to achieve the desirable energy output efficiency andutilization lifetime. Currently, commercial Pt/C catalysts are currently the most employedcathode catalysts in PEMFCs. While, the overpotential on Pt/C cathode is still high and its massactivity is still far from satisfactory. Moreover, the durability problem for this material isparticularly severe, it usually undergoes significant loss of the electrochemical surface area（ECSA） upon long-term potential scan due to corrosion of the carbon support and thedissolution/aggregation/Ostwald ripening of Pt nanoparticles. Consequently, the developmentof cathode eletrocatlysts for oxygen reduction reaction （ORR） has been one of important andintense issues for PEMFCs. Moreovr, it is known that the PEMFCs’ efficiency will significantlydegrade when the methanol permeates to the cathode side because Pt-based catalysts usuallyhave high methanol electrooxidation activity. Hence, it is of practical importance for thecathode catalyst to possess high methanol tolerance.In order to further enhance the ORR performance, decrease the catalyst cost as well asimprove the structure stability and methanol tolerance, we successfully fabricated thenanoporous PdCu alloy with three different bimetallic ratios and hierarchical nanoporous（HNP-PtCu） PtCu with bimodal ligament/pore size distributions by the method of dealloying.Nanoporous metals prepared by dealloying have some advantages with good electronconductivity, no particle aggregation, extremely clean metal surface, excellent reproducibility,and simple preparation. All of these dealloyed samples show a three-dimensional bicontinuousligament-pore nanostructures.Based on the experimental observations, by comparison with commercial Pt/C catalysts,NP-Pd₅₀Cu₅₀exhibits the highest methanol tolerance and enhanced catalytic durability for ORR.HNP-PtCu exhibits superior electrocatalytic activity for ORR with much higher structure stability besides the improved specific and mass activity. These nanomaterials thus holdpromising application potential for use as efficient cathode oxygen reduction reactionelectrocatalysts in fuel-cell-related technologies.