Enhancing photocatalytic H2 evolution of Cd0.5Zn0.5S with the synergism of amorphous CoS cocatalysts and surface S2− adsorption

Designing surface phase is an efficient strategy to facilitate charge separation and photocatalytic H₂-evolution performance. In this work, CoS cocatalysts were intimately anchored on Cd_0.5Zn_0.5S (denoted as CZS) photocatalyst via in-situ precipitate transformation in S²⁻/SO₃²⁻ solution with cobaltous phosphate (CoPi) as a precursor, meanwhile, S²⁻ ions were adsorbed on the CZS to form a sulfur-rich surface (denoted as CZS-S). The photocatalytic H₂-evolution rate of CoS/CZS-S is 2.02 mmol·g⁻¹·h⁻¹ in 0.1 M Na₂S/Na₂SO₃ sacrificial agent system. In addition, CoS/CZS-S exhibits excellent stability in both Na₂S/Na₂SO₃ and lactic acid system. The theoretical calculations (DFT) and experimental results reveal that amorphous CoS can work as a highly effective cocatalyst for H₂ evolution reaction and the intimate contact between CZS and CoS facilitates the photoelectrons transfer from CZS to CoS. The adsorbed S²⁻ ions mainly work as effective hole acceptors. As a result of the synergism of CoS and adsorbed S²⁻ ions, the boosted separation and immigration of photoelectrons and photoholes and high photocatalytic H₂-evolution performance of CoS/CZS-S are realized. The present work highlights simultaneous reinforcing reduction and oxidation half-reaction dynamics via a facile and economic surface strategy to achieve efficient solar H₂-evolution from H₂O splitting.