Black Phosphorous Mediates Surface Charge Redistribution of CoSe₂ for Electrochemical H₂O₂ Production in Acidic Electrolytes

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. © 2022 Wiley-VCH GmbH.