Investigation on the Photocatalytic Hydrogen Evolution Properties of Z-Scheme Au NPs/CuInS2/NCN-CNx Composite Photocatalysts

Aiming at precisely adjusting the interfacial electric field of the Z-scheme heterojunction to facilitate carrier transfer, we construct a new series of Au NPs/CuInS2/NCN-CNx composite photocatalysts for photosplitting water into hydrogen. By regulating the Cu vacancy via Cu/In ratios, the optimal band structure has been achieved for CuInS2/NCN-CNx samples. Au nanoparticles (NPs) are further in situ grown on CuInS2/NCN-CNx by photodeposition, which enable the light absorption range to expand to further improve light utilization due to its surface plasmon resonance (SPR) effect. With the aid of surface photovoltage (SPV), transient photovoltage (TPV), and Kevin probe force microscopy (KPFM) techniques, the carrier transfer mechanism of Au NPs/CuInS2/NCN-CNx is investigated, which can well meet the Z-scheme transfer system, and Cu deficiency regulation can slightly change the interfacial electric field from the CuInS2/NCN-CNx heterojunction. Besides, the deposition location of Au NPs is also suggested by the comparison of Au NPs photodeposited on the composite photocatalyst under full-spectrum or 550 nm irradiation, which also confirms that our CuInS2/NCN-CNx photocatalysts meet the Z-scheme mechanism. The cooperative effect of the Z-scheme transfer mechanism and the SPR effect present a H2 evolution rate of 10.72 mmol h–1 g–1 when the Pt is adopted as a cocatalyst and triethanolamine as a sacrificial reagent, about 21 times as high as that of pure NCN-CNx. Our work attempts a new way to improve the photocatalytic properties of Au NPs/CuInS2/NCN-CNx composite Z-scheme photocatalysts, which is also beneficial for designing more efficient photocatalysts for photosplitting water into hydrogen.