Bifunctional Nanostructured Palladium/MoS_x Electrocatalyst for Cathode Hydrogen Evolution Reaction PEM Water Electrolysis and Oxygen Reduction Reaction

Abstract The creation of effective Pd‐based architectures with numerous electrocatalytic active sites and efficient charge transfer is of key importance for improving the electrocatalytic performance in water electrolyzer and fuel cell applications. On the other hand, MoS₂, possessing multiple electrocatalytic active sites, can act both as support and booster to Pd‐based electrocatalytic structures. Herein, MoS_x@Pd hybrids were successfully synthesized by using a one‐pot liquid phase solvothermal strategy with stoichiometric excess of Pd. The optimized MoS_x@Pd proves to be an excellent bifunctional electrocatalyst for both hydrogen evolution reaction and oxygen reduction reaction (ORR). Optimized MoS_x@Pd operates the process for hydrogen evolution at the same potential as Pt/C and achieves a low overpotential of 76 mV at −10 mA cm⁻² due to improved reaction kinetics and charge transfer processes between Pd and MoS₂. On top of that, MoS_x@Pd exhibits excellent performance and stability as cathode electrocatalyst in a polymer electrolyte membrane water electrolyzer. Simultaneously, the bifunctional electrocatalyst shows enhanced electrocatalytic ORR activity and stability by maintaining 93% of its initial activity outperforming commercial Pt/C. Finally, rotating ring disk electrode analysis reveals that ORR proceeds through the energy efficient 4e⁻ pathway, with water being the main product, rendering MoS_x@Pd a promising component for fuel cells.