Coupling effect of (SCN)x nanoribbons on PCN nanosheets in the metal-free 2D/1D Van der Waals heterojunction for boosting photocatalytic hydrogen evolution from water splitting

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Hydrogen extraction from the water splitting driven by solar energy is considered to be a sustainable technology, but it is still a challenging issue to develop high-efficient and stable photocatalysts. Herein, a new metal-free polymeric carbon nitride (PCN)-based Van der Waals (VdW) heterojunction photocatalyst is exploited by controlling the micro-morphologies of another structural unit, the unique 2D/1D microstructure of which is fabricated by decorating polythiocyanogen (SCN)x nanoribbons on PCN nanosheets. The coupling effect of (SCN)x on PCN effectively propels interplanar charge separation through Z-scheme charge transfer path formed by the compact face-to-face π-π electronic interaction between them. Moreover, the 1D nanoribbon morphology of (SCN)x also can shorten one direction of charge migration distance in the plane to inhibit the intramolecular carrier recombination compared with traditional 2D structure. The resultant photocatalytic hydrogen evolution (PHE) rate on the optimal PCN/(SCN)x-3 % sample reaches about 4 times as large as pure PCN, and a high apparent quantum efficiency (AQE) of 18.5 % is also achieved at 420 nm. This work develops a new design approach based on spatial dimension regulation strategy of structure unit for developing PCN-based VdW heterojunction photocatalyst applied to hydrogen production from the water splitting.