Recent progress in the development of carbonate-intercalated Zn/Cr LDH as a novel photocatalyst for hydrogen evolution aimed at the utilization of solar light

Abstract

A series of novel photocatalysts Zn/Cr LDH with different Zn/Cr molar ratios (2 : 1, 3 : 1, 4 : 1 and 2 : 1–CO₃) were fabricated by a co-precipitation method and evaluated for photodecomposition of water using visible light irradiation. Various characterization methods were employed to investigate the structures, morphologies and photocatalytic properties. In comparison to Zn/Cr (2 : 1) LDH, Zn/Cr–CO₃ (2 : 1) LDH extends the absorption edges to the visible region and exhibits good photocatalytic activity, even without the assistance of co-catalysts. The visible light photocatalytic activity is ascribed to the charge transfer spectra of octahedral Cr ions in LDH. Zn/Cr–CO₃ LDH shows enhanced photocatalytic activities compared to Zn/Cr LDH as carbonate ions oxidise by holes to form carbonate radicals, inhibit the rapid recombination of e⁻ and h⁺ charge carriers and thereby suppress the backward reaction to some extent. This work provides a detailed understanding of the semiconductor properties of LDHs for photocatalytical hydrogen evolution.