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. © 2023 The Royal Society of Chemistry