Large improvement of visible-light photocatalytic H ₂-evolution based on cocatalyst-free Zn _0.5Cd _0.5S synthesized through a two-step process

Abstract

Cocatalyst-free Zn _0.5Cd _0.5S (ZnCdS-CH) is synthesized through a two-step process as a highly active and stable photocatalyst for visible-light hydrogen evolution.

Abstract

Final metal sulfides Zn _0.5Cd _0.5S (ZnCdS-CH) are synthesized through a coprecipitation process followed by hydrothermal treatment. The morphological, structural and optical properties have been investigated extensively viadiverse analytical techniques. The ZnCdS-CH solid solution without noble metal loading is employed in photocatalytic H ₂evolution under visible light irradiation ( λ≥ 420 nm) and achieves a superior activity rate of 0.971 mmol h ⁻¹, which exceeds those of coprecipitated Zn _0.5Cd _0.5S (ZnCdS-C) samples by more than 13 times. Moreover, in the recycle test, the ZnCdS-CH photocatalyst shows a stable photocatalytic activity for H ₂evolution under long-term visible-light irradiation. Characterization analyses demonstrate that the excellent photocatalytic H ₂-evolution performance of the ZnCdS-CH sample arises predominantly from the two-step processing procedure of coprecipitation followed by hydrothermal treatment at 200 °C, which makes it possess a hexagonal (wurtzite) structure, good dispersity, enhanced crystallinity, an appropriate band gap, a more negative conduction band, as well as a large number of surface defect states. This finding is of great significance for designing a facile, reproducible and inexpensive method to realise the potential of Zn _xCd _1−xS ternary metal sulfides in the field of H ₂evolution by water splitting.