Stable Pentagonal Layered Palladium Diselenide Enables Rapid Electrosynthesis of Hydrogen Peroxide.

Electrosynthesis of hydrogen peroxide (H 2 O 2 ) 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 PdSe 2 with a unique pentagonal puckered ring structure type. Computations predict active and selective 2e - ORR on the basal plane and edge of PdSe 2 , but with distinct kinetic behaviors. Electrochemical measurements of hydrothermally synthesized PdSe 2 nanoplates show a higher 2e - ORR activity than other Pd-Se compounds (Pd 4 Se and Pd 17 Se 15 ). PdSe 2 on a gas diffusion electrode can rapidly accumulate H 2 O 2 in buffered neutral solution under a high current density. The electrochemical stability of PdSe 2 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.