Two-dimensional-layered heterojunctions have attracted extensive interest recently due to their exciting behaviours in electronic/optoelectronic devices as well as solar energy conversion systems. However, layered heterojunction materials, especially those made by stacking different monolayers together by strong chemical bonds rather than by weak van der Waal interactions, are still challenging to fabricate. Here the monolayer Bi2WO6 with a sandwich substructure of [BiO]+–[WO4]2−–[BiO]+ is reported. This material may be characterized as a layered heterojunction with different monolayer oxides held together by chemical bonds. Coordinatively unsaturated Bi atoms are present as active sites on the surface. On irradiation, holes are generated directly on the active surface layer and electrons in the middle layer, which leads to the outstanding performances of the monolayer material in solar energy conversion. Our work provides a general bottom-up route for designing and preparing novel monolayer materials with ultrafast charge separation and active surface.

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A marigold-like SiC@MoS 2 nanoflower with a unique Z-scheme structure efficiently achieves the overall conversion of gas phase CO 2 with H 2 O (CO 2 (g) + 2H 2 O (g) = CH 4 + 2O 2 ) without any sacrificial reagents under visible light (λ ≥ 420 nm) irradiation. The CH 4 and O 2 evolution are 323 and 621 μL•g −1 •h −1 , and stable throughout 5 cycle reactions of total 40 h. This work demonstrates a breakthrough in artificial photosynthesis with the Z-scheme 1D heterojunction constructed by combining 2D semiconductor and 3D semiconductor based on the transfer balance of photogenerated electron and hole.

The stoichiometric photocatalytic reaction of CO 2 with H 2 O is one of the great challenges in photocatalysis. Here, we construct a Cu 2 O-Pt/SiC/IrO x composite by a controlled photodeposition and then an artificial photosynthetic system with Nafion membrane as diaphragm separating reduction and oxidation half-reactions. The artificial system exhibits excellent photocatalytic performance for CO 2 reduction to HCOOH and H 2 O oxidation to O 2 under visible light irradiation. The yields of HCOOH and O 2 meet almost stoichiometric ratio and are as high as 896.7 and 440.7 μmol g −1 h −1 , respectively. The high efficiencies of CO 2 reduction and H 2 O oxidation in the artificial system are attributed to both the direct Z-scheme electronic structure of Cu 2 O-Pt/SiC/IrO x and the indirect Z-scheme spatially separated reduction and oxidation units, which greatly prolong lifetime of photogenerated electrons and holes and prevent the backward reaction of products. This work provides an effective and feasible strategy to increase the efficiency of artificial photosynthesis.

Copolymerization with 2,4,6-triaminopyrimidine (TAP) is developed for precise substitution of one nitrogen with carbon atom in the triazine ring of polymeric g-C3N4. Direct incorporation of C4N2 ring from TAP into the network retains the structural features of g-C3N4, but induces the rolling-up of g-C3N4 sheets into tubular configuration. The band gap energy is narrowed from 2.7 to 2.4 eV by a negative shift of valence band of the g-C3N4 photocatalyst, which enhances charge-carrier migration and separation, leading to higher photocatalytic activity for NO gas pollutant removal. It is attributed to the decrease of the π-deficiency and the generation of imbalanced electron density in π-electron conjugated units of g-C3N4 by TAP incorporation. This work provides a significant technique for precise control of heteroatom in the framework of g-C3N4 to finely adjust its intrinsic electronic properties and its photocatalytic properties.