The challenge in the artificial photosynthesis of fossil resources from CO by utilizing solar energy is to achieve stable photocatalysts with effective CO 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 CO to CO, yielding a CO evolution rate of 27.2 µmol g h without cocatalyst and sacrifice reagent, which is >2.2 times higher than that produced by g-C N alone (10.3 µmol g h ). 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 CO 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-C N . 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 CO 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.

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Here we present a new visible light active composite based on porous graphitic carbon nitride decorated hierarchical yolk–shell TiO2 spheres for water pollution treatment and H2 evolution.