Function of NiSe2 over CdS nanorods for enhancement of photocatalytic hydrogen production - From preparation to mechanism

Noble metal-free NiSe2 nanoparticles as co-catalyst to modify CdS nanorods for enhancement hydrogen evolution was successfully synthesized by semi-solid reaction method and heterogenous NiSe2/CdS nanorods arrays were fabricated by using a facile successive ionic adsorption under phase-change environment. With the introduction of NiSe2, the H-2 production of 30% NiSe2/CdS photocatalyst reached the peak value about 61522 mu mol/g under continuous visible light irradiation for 5 h, which was 2.6 times higher than that of the pure CdS photocatalyst. Moreover, cyclic experiments exhibited that the composite catalyst has excellent stability. The possible detail enhancement mechanism was speculated and discussed by morphological, optical and electrochemical characterization such as SEM, TEM, XRD, EDS, BET, XPS, UV-vis DRS, PL spectrum, LSV, EIS and etc. All results showed good consistency. Based on it, we speculated the heterojuction formed with special VB and CB of CdS and NiSe2 caused efficient charge separation and lowed the over potential of H+ reduction. NiSe2 co-catalyst loaded on the surface of CdS nanorods, which not only blocked the CdS from photocorrosion, but also provided an electron transfer medium which transfers photogenerated electrons from CdS to NiSe2 surface rapidly, enhancing the photocatalytic hydrogen evolution.