Nickel-Based Bifunctional Cocatalyst to Enhance CdS Photocatalytic Hydrogen Production

The design of nanocomposites as a light-capturing system applied in photocatalytic water splitting is an emerging area of research. In our study, a simple in situ photodeposition method was proposed for the synthesis of CdS nanoflowers modified by nickel-based bifunctional, i.e., Ni/Ni(OH)₂, cocatalysts. The introduction of cocatalysts has demonstrated a notable enhancement in the photocatalytic hydrogen evolution efficiency of CdS. The quantity of cocatalysts supported on CdS played an important role in governing the light absorption capability and photocatalytic efficacy. Ni-CdS-10 showed the best photocatalytic activity of 30.51 mmol g^-1 h^-1, which was 1.8 times and 2.6 times higher activity than Pt-CdS-1 wt % and pure CdS, respectively. Mechanism studies with UV-vis DRS, photoluminescence, and Mott-Schottky plots revealed the intrinsic electric field created at the p-n Ni(OH)₂/CdS junctions, which can effectively implement the transport and separation of photoinduced carriers. From linear sweep voltammetry, electrochemical impedance spectroscopy, and DFT calculation, both Ni(OH)₂ and Ni can effectively decrease the Gibbs free energies of hydrogen adsorption and reduce the overpotential of hydrogen evolution. As a result, the efficiency of generating H₂ through photocatalysis experienced significant improvement, and the participation of bifunctional cocatalysts further reduced the photocorrosion of CdS, enhanced stability, improved low price, and efficient photocatalyst production.