Abstract
The challenge in the artificial photosynthesis of fossil resources from CO2 by utilizing solar energy is to achieve stable photocatalysts with effective CO2 adsorption capacity and high charge-separation efficiency. A hierarchical direct Z-scheme system consisting of urchin-like hematite and carbon nitride provides an enhanced photocatalytic activity of reduction of CO2 to CO, yielding a CO evolution rate of 27.2 µmol g−1 h−1 without cocatalyst and sacrifice reagent, which is >2.2 times higher than that produced by g-C3N4 alone (10.3 µmol g−1 h−1). The enhanced photocatalytic activity of the Z-scheme hybrid material can be ascribed to its unique characteristics to accelerate the reduction process, including: (i) 3D hierarchical structure of urchin-like hematite and preferable basic sites which promotes the CO2 adsorption, and (ii) the unique Z-scheme feature efficiently promotes the separation of the electron–hole pairs and enhances the reducibility of electrons in the conduction band of the g-C3N4. The origin of such an obvious advantage of the hierarchical Z-scheme is not only explained based on the experimental data but also investigated by modeling CO2 adsorption and CO adsorption on the three different atomic-scale surfaces via density functional theory calculation. The study creates new opportunities for hierarchical hematite and other metal-oxide-based Z-scheme system for solar fuel generation.
A hierarchical direct Z-scheme hybrid for the photocatalytic reduction of CO2 without using any sacrifice agent or cocatalyst is developed by combining urchin-like α-Fe2O3 and g-C3N4. The coupling of the urchin-like α-Fe2O3 with g-C3N4 can trigger significantly improved photoreduction activity of CO2 to form CO.
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