Strongly Coupled Cobalt Diselenide Monolayers for Selective Electrocatalytic Oxygen Reduction to H₂O₂ under Acidic Conditions

Electrosynthesis of hydrogen peroxide (H₂ O₂ ) in the acidic environment could largely prevent its decomposition to water, but efficient catalysts that constitute entirely earth-abundant elements are lacking. Here we report the experimental demonstration of narrowing the interlayer gap of metallic cobalt diselenide (CoSe₂ ), which creates high-performance catalyst to selectively drive two-electron oxygen reduction toward H₂ O₂ in an acidic electrolyte. The enhancement of the interlayer coupling between CoSe₂ atomic layers offers a favorable surface electronic structure that weakens the critical *OOH adsorption, promoting the energetics for H₂ O₂ production. Consequently, on the strongly coupled CoSe₂ catalyst, we achieved Faradaic efficiency of 96.7 %, current density of 50.04 milliamperes per square centimeter, and product rate of 30.60 mg cm⁻² h⁻¹ . Moreover, this catalyst shows no sign of degradation when operating at -63 milliamperes per square centimeter over 100 hours.