Effects of composition faults in ternary metal chalcogenides (ZnxIn2S3+x, x=1-5) layered crystals for visible-light-driven catalytic hydrogen generation and carbon dioxide reduction

Exploring efficient and stable photocatalysts is critical for the practical application of photocatalytic water splitting to get clean hydrogen fuel. In this work, ZnxIn2S3+x (x = 1-5) samples with various composition faults were synthesized through a simple hydrothermal method as a series of highly efficient visible-light-driven photocatalysts. Composition faults in ZnxIn2S3+x samples played important roles in the charge carrier transfer from internal to external surfaces, further affecting the redox reaction of photogenerated electrons and holes at the solid-liquid interface. The absorption edge of ZnxIn2S3+x samples shifted to shorter wavelengths as the atomic ratio of Zn/In in the synthetic solution was increased (i.e., x increased from 1 to 5). The photocatalytic activity of ZnxIn2S3+x was evaluated via photocatalytic hydrogen production from water and CO2 reduction under visible light irradiation. The obtained ZnIn2S4 (x = 1) sample displayed the best photocatalytic activity among the ZnxIn2S3+x photocatalysts, with the hydrogen evolution rate determined to be 2.93 mmol.h(-1)g(-1) and the quantum yield at 420 nm determined to be 7.92%. As for visible light-driven CO2 reduction, the ZnxIn2S3+x sample also exhibited the highest CO formation rate of 40.4 mu mol h(-1)g(-1). Results suggest that the existence of composition faults provided extra energy barriers to block photoinduced charge carrier transfer. Furthermore, the cyclic tests indicate the stability of the ZnIn2S4 product over five cycles of repeated use. This study provides new insights into unveiling the relationship of structure-property of ZnxIn2S3+x layered crystals, which are valuable for implementation in a wide range of environmental energy applications.