Periodic quantum well mediated oriented charge separation in Cd0.3Zn0.7S twin crystal towards optimized photocatalytic hydrogen evolution
Interface engineering is vital for promoting charge separation in photocatalysis. Herein, a twin crystal interface in Cd 0.3 Zn 0.7 S is engineered, which leads to a variation of the electric polarization along the interface and the formation of a periodic quantum well along z axis. The periodic quantum well could effectively facilitate the oriented charge separation and significantly reduce the diffusion distance simultaneously. Density functional theory (DFT) calculations confirm that Cd 0.3 Zn 0.7 S twin crystal possesses a relative low work function and an appropriate hydrogen adsorption Gibbs free energy (ΔG H* ), making each step of the cascaded hydrogen evolution reactions optimized. As a result, the resultant twin crystal exhibits an excellent visible light photocatalytic hydrogen evolution rate (13148.98 μmol·g −1 ·h −1 ), which is almost 10 and 30 times higher than those of CdS and ZnS. Importantly, it also shows a good stability because of the formation of twin crystal interface. In addition, the introduction of S vacancy defect results in narrowing the band gap and extending the photo-response to long wavelength region. Such a twin crystal interface engineering strategy provides a basic guideline for designing high-efficient photocatalysts with tunable electric polarization.
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