Light-assisted synthesis MoSx as a noble metal free cocatalyst formed heterojunction CdS/Co3O4 photocatalyst for visible light harvesting and spatial charge separation

Abstract

In this paper, a novel photocatalyst with visible light harvesting and spatial charge separation is reported, in which cobalt oxide (acting as a hole trap) and molybdenum sulfide (acting as an electron trap) are assembled on the surface of cadmium sulfide nanorods. The MoS_x/CdS/Co₃O₄ composite photocatalyst shows a high H₂ evolution with a yield of 537.51 μmol in 5 h, which is 35.53 times greater than over pristine CdS (15.13 μmol). The detailed underlying reason was comprehensively studied and understood by means of SEM, TEM, XRD, XPS, UV-vis DRS, BET; in particular, investigation of their photoelectrochemical properties with photocurrent, voltammetric scanning, fluorescence spectra etc. The high photocurrent response, the lower overpotential (−0.37 V vs. SCE), the faster electron transfer rate constant (k_et = 4.23 × 10⁹ s⁻¹) and the short fluorescence lifetime (0.457 ns) supported the efficient spatial charge transfer between CdS and MoS_x as well as Co₃O₄. The simultaneous loading of bicocatalysts can significantly improve the photo-induced spatial charge separation of CdS because MoS_x nanoparticles act as an electron trap to rapidly transfer electrons from CdS while Co₃O₄ acts as a hole trap to quickly transfer holes, enhancing its photocatalytic performance as well.