Interface engineering of ZnO/In2O3 Z-scheme heterojunction with yolk-shell structure for efficient photocatalytic hydrogen evolution

Photocatalytic activities based on charge transfer and separation at interfaces can be effectively promoted by matching chemical Z-scheme heterojunctions and electronic structures. However, the fabrication of morphology-controlled heterojunctions has been a challenge to many researchers. Herein, hollow spheres ZnO/In2O3 was constructed via hydrothermal strategy by fine-tuning the concentration of metal nitrate precursors, and special yolk-shell morphology was generated by the symmetrical Ostwald ripening process. The fabricated Z-Scheme heterojunction exhibited characteristic multi-channel charge transfer properties, which favors the spatial separation of carriers. The ZnO/In2O3 hollow spheres increased the utilization of light source, and the yolk-shell structure increased the interface area and the active sites. Benefiting from the synergistic effect, the ZnO/In2O3 exhibited excellent photocatalytic activities for H2 production, which was comparatively 26.7 times that obtained using ZnO nanoparticles. From calculations based on DFT, the Z-scheme photogenerated charge transfer mechanism was proposed. The proposed mechanism was verified by analyzing the chemical properties (surface) and the •O2− and •OH free radical concentrations before and after the photoreaction. The mechanism presented the ZnO/In2O3 with strong capabilities for H2 production and elucidated the improved photocatalytic performances. This work creates an innovative route for constructing Z-scheme photocatalytic systems with great photocatalytic activities for H2 production.