Abstract:

Two-dimensional mesoporous ultrathin Cd_0.5Zn_0.5S nanosheets with a thickness of ~1.5 nm were fabricated using a multistep chemical transformation strategy involving inorganic-organic hybrid ZnS-ethylenediamine (denoted as ZnS(en)_0.5) as a hard template. Inorganic-organic hybrid ZnS(en)_0.5, Cd_0.5Zn_0.5S(en)_x, and Cd_0.5Zn_0.5S nanosheets were sequentially fabricated, and their transformation processes were analyzed in detail. The fabricated Cd_0.5Zn_0.5S nanosheets exhibited high photocatalytic hydrogen evolution reaction activity in the presence of a sacrificial agent. The Cd_0.5Zn_0.5S nanosheets exhibited remarkably high H₂ production activity of ~1395 μmol∙h^-1∙g^-1 in pure water with no co-catalyst, which is the highest value reported thus far for bare photocatalysts, to the best of our knowledge. The high activity of these nanosheets is attributed to their distinct nanostructure (e.g., short transfer distance of photoinduced charge carriers, large number of unsaturated surface atoms, and large surface area). Moreover, ternary NiCo₂S₄ nanoparticles were employed to facilitate the charge separation and enhance the surface kinetics of H₂ evolution. The H₂ production rate reached ~62.2 and ~2436 μmol∙h^-1∙g^-1 in triethanolamine and pure water, respectively, over the NiCo₂S₄/Cd_0.5Zn_0.5S heterojunctions. The result indicated that the Schottky junction was critical to the enhanced activity. The proposed method can be used for fabricating other highly efficient CdZnS-based photocatalysts for solar-energy conversion or other applications.

Key words: Mesoporous, Ultrathin, Cd_0.5Zn_0.5S nanosheets, Photocatalysis, Hydrogen evolution