Novel design of mesoporous step-scheme CuMn2O4/ZnWO4 photocatalyst for visible-light-induced H2 evolution: Enhancing charge separation and expanding light photon absorption

The development of sophisticated step (S)-type heterojunctions has become fundamental in the quest for the production of sustainable hydrogen. Herein, for the first time, novel mesoporous S-type CuMn₂O₄/ZnWO₄ (CMO/ZWO) heterostructured photocatalysts were constructed with diverse CMO contents through a facile wet impregnation approach for visible-light-driven hydrogen evolution from a glycerol-water mixture in the presence of a co-catalyst (Pt), which was in situ loaded on the photocatalyst surface during the reactions. For achieving H₂ generation effectively, platinum (Pt), as a typical co-catalyst, has been utilized to overcome the considerable overpotential. Moreover, Pt co-catalyst can capture the photon-excited e⁻s from the photocatalyst surface. Meanwhile glycerol (a biomass-derived substance) was served as scavenger for the photon-excited h⁺s, providing protons (H⁺s), which can be reduced by the photon-excited e⁻s into H₂ gas with the assistance of Pt. The most effective heterostructured photocatalyst, 9 % CMO/ZWO, showcased an extensive surface area (117 m²/g), a two-dimensional (2D) skeleton, mesoporous qualities, an improved absorbing border (479.6 nm), and a relatively small band gap (2.66 eV). Moreover, the 9 % CMO/ZWO achieved substantial capability to separate photon-excited charge (electron/hole: e⁻/h⁺) pairs along with significant redox capacities. Hence, the 9 % CMO/ZWO generated an H₂ amount of 32.66 (±1.633) mmol g⁻¹ from, with an optimized rate of 4.16 (±0.208) mmol h⁻¹ g⁻¹, surpassing that attained utilizing bare CMO and bare ZWO by about 12.2 and 139 times, individually. Five-cycle experiments also unveiled the significant stability of 9 % CZ. The main reason for this impressive effectiveness is the development of the S-scheme heterostructure, which improved the separation of photon-excited charges, increased the ability to capture and use visible light, and enhanced the redox capacities. This research shows an innovative, practical way to create better S-scheme heterojunction photocatalysts for producing hydrogen from water efficiently and reliably.