LAUSR

Electrochemical generation of hydrogen peroxide (H2O2) by two‐electron oxygen reduction offers a green method to mitigate the current dependence on the energy‐intensive anthraquinone process, promising its on‐site applications. Unfortunately, in alkaline environments, H2O2 is not stable and undergoes rapid decomposition. Making H2O2 in acidic electrolytes can prevent its decomposition, but choices of active, stable, and selective electrocatalysts are significantly limited. Here, the selective and efficient two‐electron reduction of oxygen toward H2O2 in acid by a composite catalyst that is composed of black phosphorus (BP) nailed chemically on the metallic cobalt diselenide (CoSe2) surface is reported. It is found that this catalyst exhibits a 91% Faradic efficiency for H2O2 product at an overpotential of 300 mV. Moreover, it can mediate oxygen to H2O2 with a high production rate of ≈1530 mg L−1 h−1 cm−2 in a flow‐cell reactor. Spectroscopic and computational studies together uncover a BP‐induced surface charge redistribution in CoSe2, which leads to a favorable surface electronic structure that weakens the HOO* adsorption, thus enhancing the kinetics toward H2O2 formation.