Construction of 2D/2D Ni2P/CdS heterojunctions with significantly enhanced photocatalytic H2 evolution performance
Two-dimensional (2D) materials have received tremendous attentions in photocatalysis owing to their superior physicochemical properties including high specific surface areas, efficiently interfacial charge separation and abundant surface active sites. Herein, 2D/2D Ni2P/CdS heterojunctions with Ni2P nanosheets (NSs) loaded on ultrathin CdS NSs were fabricated by combining liquid exfoliating bulk CdS with post-annealing procedure. The crystal phases, morphologies, microstructures, optical properties and specific surface areas of as-prepared photocatalysts were thoroughly investigated by multiple detection techniques. The results of photocatalytic H2 evolution performance under visible light revealed that the optimal 2D/2D Ni2P/CdS heterojunction showed a significantly enhanced photocatalytic H2 evolution rate of 17.95 mmol g-1 h-1 using lactic acid as sacrificial reagent, which was approximately 6 times higher than that of bare exfoliated CdS NSs, corresponding to the apparent quantum efficiency (AQE) of 4.2% at 420 nm monochromatic light. In addition, based on the analysis of electrochemical impedance spectroscopy (EIS), photocurrent response, steady photoluminescence spectra (PL) and time-resolved photoluminescence (TRPL) spectra, the enhanced photocatalytic H2 evolution activity was attributed to the effective separation and transfer of photogenerated charge carriers, and sufficient active sites. This work provided a valid evidence that construction of 2D/2D heterojunction photocatalysts would be a promising technique in splitting water for H2 generation.