Black Phosphorous Mediates Surface Charge Redistribution of CoSe₂ for Electrochemical H₂ O₂ Production in Acidic...

Electrochemical generation of hydrogen peroxide (H₂ O₂ ) 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, H₂ O₂ is not stable and undergoes rapid decomposition. Making H₂ O₂ 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 H₂ O₂ 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 H₂ O₂ product at an overpotential of 300 mV. Moreover, it can mediate oxygen to H₂ O₂ 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 H₂ O₂ formation.