NiCoP as a cocatalyst decorating CdIn2S4 for enhanced photocatalytic performance under visible light: DFT calculation and mechanism insight

Solar photocatalysis, a green and sustainable technology, can effectively address the global energy shortage and environmental pollution. Herein, CdIn2S4 (CIS) microflowers and NiCoP (NCP) nanoparticles were prepared by hydrothermal synthesis and vacuum calcination, respectively. Subsequently, novel NiCoP/CdIn2S4 (abbreviated x wt % NCP/CIS; x = 7, 9, 11, 13, and 15) composite photocatalysts were synthesized using an impregnation method. The as-obtained NCP/CIS catalysts exhibited excellent photocatalytic activities for hydrogen production and Cr(VI) reduction with high cycling stability under visible light (λ > 420 nm). The H2 production rate of the optimal 11% NCP/CIS sample was 651.67 μmol g−1 h−1, which was approximately 25.92 times higher than that of individual CIS (25.14 μmol g−1 h−1). The apparent quantum efficiency at 420 nm reached 3.31%. The rate constant of photocatalytic Cr(VI) reduction reached 0.036 min−1, 2.77 and 11.19 times that of CIS (0.013 min−1) and NCP (0.0032 min−1), respectively. The enhanced photocatalytic properties of NCP/CIS are attributed to the improved visible-light absorption and efficient separation of photoinduced carriers. Furthermore, free radical capturing tests and ESR data proved that e− and ·O2− were responsible for Cr(VI) reduction. The electron transfer pathway and photocatalytic mechanism were verified using X-ray photoelectron spectroscopy, density functional theory calculations, and energy band structures. This study provides novel approaches for designing and preparing non-noble metal cocatalyst/semiconductor systems with remarkably efficient photocatalytic performance for Cr(VI) removal and H2 generation.