An in situ-fabricated p-Co3O4@n-ZnO surface heterojunction photocatalyst for solar-to-fuel conversion of CO2

The development of commercially promising ZnO-based photocatalysts for CO2 reduction without photosensitizers and scavengers has encountered bottlenecks due to low photon utilization and easy recombination of photoexcited electron-hole pairs. Herein, a p-Co3O4@n-ZnO surface heterojunction photocatalyst (simplified as Co3O4@ZnO), composed of ZnO nanorods surface-synergized with Co3O4 nanosheets, has been constructed for efficient CO2 photoreduction using a facile in situ solution-fabricated approach. The resulting Co3O4@ZnO demonstrates a dramatic 36-fold higher catalytic activity (89.26 mu mol g(-1) h(-1)) than pristine ZnO (2.44 mu mol g(-1) h(-1)) under simulated sunlight, with a long-term durability of 30 h. Various characterizations and finite difference time domain simulations reveal that the formed Co3O4@ZnO surface p-n heterojunctions expand the light absorption range, promote the separation of photocarriers, and accelerate the charge transport, thereby benefiting the photocatalytic efficiency and stability. In addition, on the surface of heterojunctions, the accumulated electrons and adsorbed protons further encourage the evolution of CH4 products, which makes the CH4 selectivity of Co3O4@ZnO (70.5%) far exceed that of pristine ZnO (12.4%). This work provides guidance in the fabrication of efficient and convenient heterojunction photocatalysts for CO2 conversion into carbon fuels, and is anticipated to promote the popularization and application of ZnO-based photocatalysts.