Stable Pentagonal Layered 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 are also resistant to catalyst leaching under realistic operating conditions. Here, a joint experimental and computational study reveals active and stable 2e^- ORR catalysis in neutral media over layered PdSe₂ with a unique pentagonal puckered ring 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 a higher 2e^- ORR activity than other Pd-Se compounds (Pd₄Se and Pd₁₇Se₁₅). PdSe₂ on a gas diffusion electrode can rapidly accumulate H₂O₂ in buffered neutral solution under a high current density. The electrochemical stability of PdSe₂ is further confirmed by long device operational stability, elemental analysis of the catalyst and electrolyte, and synchrotron X-ray absorption spectroscopy. This work establishes a new efficient and stable 2e^- ORR catalyst at practical current densities and opens catalyst designs utilizing the unique layered pentagonal structure motif.