Preparation Of Nanoporous Pd-based Bimetallic Material And Study On The Oxygen Reduction Reaction Performance

Proton exchange membrane fuel cells(PEMFCs) have showed great application prospect owing to their great application potential as alternative energy sources in the fields of automotive systems and portable electronics. Oxygen reduction reaction(ORR) occurred at the cathode is significant for PEMFCs to achieve the desirable energy output efficiency and utilization lifetime. At present, commercial Pt/C catalysts are the most employed cathode catalysts for oxygen reduction in PEMFCs. While the activity of oxygen reduction cannot be satisfactory,moreover, the methanol tolerance and structure stability for ORR catalysts is severe. Consequently, the exploration of high-performance and low-cost non-Platinum eletrocatalysts for ORR has been current research focus in the cathode catalyst.In this paper, nanoporous Pd-based alloys were prepared by dealloying method, mainly included PdFe, PdCr, and PdPt alloy. Their structure were also characterized by means of XRD, SEM, TEM, XPS, etc. It could be known that the prepared PdFe, PdCr, and PdPt samples show three-dimensional bicontinuous network nanostructures. The prepared alloy materials are uniform single-phase alloy material, the surface electronic structure has changed, which is beneficial to the improvement of the ORR performance.Electrocatalytic performance(oxygen reduction reaction, catalytic stability, methanol tolerance, etc.) of prepared nanoporous materials were tested by electrochemical methods, the results exhibited that nanoporous PdFe, PdCr, and PdPt alloys exhibits superior ORR performance with much better structural durability and catalytic activity than commercial Pt/C catalysts as well as high methanol tolerance. Among nanoporous PdPt catalyst, Pd75Pt25 catalyst exhibits the highest electrical catalytic properties.Based on the experimental results and theoretical calculation, the change of the electronic structure and the surface state of Pd upon alloying 3d metals with Pd was explored, and the origin for improving the performance of ORR was further discovered. The calculation result shows that the electronic structure on the surface of the Pd has changed upon alloying Pd with Fe or Cr, which cause oxygen adsorption energy of Pd reduced, and improve the performance of ORR of Pd.