Direct Z-Scheme 2D/2D Photocatalyst Based on Ultrathin g-C3N4 and WO3 Nanosheets for Efficient Visible-Light-Driven H2 Generation

Ultrathin two-dimensional (2D) nanomaterials can not only boost the interfacial charge migration and separation but also provide abundant reactive sites for the photocatalytic H2 generation. Herein, a kind of direct Z-scheme 2D/2D hybrid nanomaterial is fabricated by post-annealing atomically ultrathin Pt-loaded g-C3N4 nanosheets (Pt-CN NSs) with a thickness of ∼4.0 nm and hydrogen-treated WO3 nanosheets (HWO NSs) with a thickness of ∼2.6 nm. The strong affinity existing between the two types of nanosheets with few-layer stacking results in the formation of atomically ultrathin 2D/2D hybrid nanomaterials (Pt-CN/HWO) with intimate interfacial contact in which the strong electronic interaction and efficient charge separation lead to a direct Z-scheme electron flowing from HWO NSs to CN NSs and then to the Pt cocatalyst for catalyzing the H2 generation reaction. After optimizing the component ratio, the corresponding Pt-CN/HWO hybrid nanomaterial delivers a significantly boosted photocatalytic H2 generation activity, up to 6.2 times as high as that of the Pt-CN/WO composite containing Pt-CN NSs and WO3 nanoplates (WO NPs) without hydrogen treatment. This result reveals that the atomically ultrathin nanosheets in the 2D/2D hybrid nanomaterials can not only deliver strong electronic interaction to promote the Z-scheme mechanism for maintaining the high reduction ability of g-C3N4 and high oxidation ability of WO3 but also alleviate the charge recombination, therefore resulting in the excellent photocatalytic H2 generation performance.