Black Phosphorous Mediates Surface Charge Redistribution of CoSe 2 for Electrochemical H 2 O 2 Production in Acidic Electrolytes.

Electrochemical generation of hydrogen peroxide (H 2 O 2 ) 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, H 2 O 2 is not stable and undergoes rapid decomposition. Making H 2 O 2 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 H 2 O 2 in acid by a composite catalyst that is composed of black phosphorus (BP) nailed chemically on the metallic cobalt diselenide (CoSe 2 ) surface is reported. It is found that this catalyst exhibits a 91% Faradic efficiency for H 2 O 2 product at an overpotential of 300 mV. Moreover, it can mediate oxygen to H 2 O 2 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 CoSe 2 , which leads to a favorable surface electronic structure that weakens the HOO* adsorption, thus enhancing the kinetics toward H 2 O 2 formation.