Novel MnS/(In$_{x}$Cu$_{1-x}$)$_{2}$S$_{3}$ composite for robust solar hydrogen sulphide splitting via the synergy of solid solution and heterojunction

Abstract

Large photocatalytic hydrogen (H$_{2}$) production from copious waste hydrogen sulphide (H$_{2}$S) can meet the increasing demand for H$_{2}$ in a sustainable manor which is beneficial from both environmental and energy standpoints. In this work, we reported a robust MnS/(In$_{x}$Cu$_{1-x}$)$_{2}$S$_{3}$ composite photocatalyst. Both experimental results and density functional theory (DFT) calculations proved that Cu does not act as a cocatalyst but forms a solid solution ((In$_{x}$Cu$_{1-x}$)$_{2}$S$_{3}$) in the composites, which plays dual roles in improving the photocatalytic performance of H2S splitting: (i) enhancing solar light absorption, and (ii) promoting the desorption of sulfur (S) adsorbed on the catalyst surface. Moreover, the formation of a heterojunction between γ-MnS and (In$_{x}$Cu$_{1-x}$)$_{2}$S$_{3}$ can significantly improve charge separation and migration in the composites. As a result, the MnS/(In$_{x}$Cu$_{1-x}$)$_{2}$S$_{3}$ exhibits greatly extended visible light absorption up to 599 nm and extraordinarily high photocatalytic H$_{2}$ production under visible light from H$_{2}$S with a maximum rate of 29,252 μmol h$^{-1}$ g$^{-1}$. The corresponding apparent quantum efficiencies (AQE) at 420 and 450 nm are as high as 65.2% and 62.6%, respectively. They are the highest so far for the visible light photocatalytic splitting of H$_{2}$S in the absence of noble-metal co-catalysts