Mechanistic insights into enhanced photocatalytic H2O2 production induced by a Z-scheme heterojunction of copper bismuth oxide and molybdenum sulfide

Abstract

Photocatalysts suffer from limited light absorption and rapid electron–hole recombination which can be overcome by fabricating a suitable Z-scheme heterojunction. A facile hydrothermal process is employed to synthesize copper bismuth oxide and molybdenum disulfide (CBO@MoS₂) composites which show a significantly high hydrogen peroxide (H₂O₂) production rate of 1457 μM h⁻¹, which is an order of magnitude higher than that exhibited by their pure components. In addition, the hydrogen evolution reaction exhibited a current density of −1.6 mA cm⁻² at 0.1 V which is also double than that exhibited by pure CBO. The improved photocatalytic activity of CBO@MoS₂ is mainly attributed to the efficient separation of electron–hole pairs due to the staggered band alignment and the formation of a Z-scheme heterojunction that retains the strong redox ability of both CBO and MoS₂. A detailed study using a superoxide scavenger indicates that the production of H₂O₂ takes a two-step route. Photoluminescence, Mott–Schottky analysis, scavenger study and kinetic modelling led to an understanding of the mechanistic aspects of H₂O₂ production.