Electroactivity of Hydrogen Oxidation Reaction on Mixed-Phase Pt_xPd_1-x@SnO₂/C Catalyst in Alkaline Electrolyte

Sluggish hydrogen oxidation reaction (HOR) kinetics at the anode of alkaline anion-exchange membrane fuel cells limit their widespread applications. In this study, a new type of Pt_xPd_1-x@SnO₂/C catalyst was designed for alkaline HOR. The electrochemical HOR kinetics was explored by potentiodynamic and electrochemical impedance spectroscopy methods supported by density functional theory (DFT). The composition of Pt and Pd in the catalyst was optimized and the highest HOR exchange current density (j₀) of 0.414 mA cm⁻²_Pt+Pd was measured using Pt_0.5Pd_0.5@SnO₂/C catalyst. This value is 4.3× and 15.9 × higher than commercial Pt/C and Pd/C, respectively, measured under same conditions. DFT calculations were performed to identify possible adsorption sites for H₂ and their adsorption energies, changes in H adsorption Gibbs free energy, overpotential (36 mV), and electronic properties. Based on electrochemical CO stripping experiments and DFT Bader charge distribution, the enhanced HOR activity is attributed to the oxophilic effect provided by SnO₂ and electron transfer from metals (Pd and Pt) to the SnO₂ cluster. An H₂-O₂ AEMFC assembled with Pt_0.5Pd_0.5@SnO₂/C anode showed the practical application in device.