Highly Stable Pentagonal 2D Palladium Diselenide Enables Rapid Electrosynthesis of Hydrogen Peroxide

Electrosynthesis of hydrogen peroxide (H₂O₂) via the two-electron oxygen reduction reaction (2e^- ORR) is promising for various practical applications such as wastewater treatment. However, few electrocatalysts are active and selective for 2e^- ORR yet also resistant to catalyst leaching under realistic operating conditions. Here, a joint experimental and computational study reveals highly active and stable 2e^- ORR catalysis in neutral media over 2D layered PdSe₂ with a unique pentagonal layered structure type. Computations predict active and selective 2e^- ORR on the basal plane and edge of PdSe₂, but with distinct kinetic behaviors. Electrochemical measurements of hydrothermally synthesized PdSe₂ nanoplates show higher 2e^- ORR activity than Pd₄Se and Pd₁₇Se₁₅, suggesting unique performance enabled by the PdSe₂ structure type. PdSe₂ on a gas diffusion electrode can rapidly accumulate H₂O₂ in a buffered neutral solution under high current density. Elemental analysis of the catalyst and electrolyte and synchrotron X-ray absorption spectroscopy confirm the chemical stability of PdSe₂under these practical electrosynthesis conditions. This work establishes a new efficient 2e^- ORR catalyst with high intrinsic stability at practical current densities and opens catalyst designs utilizing the unique 2D pentagonal structure motif.