Overview and challenges of the photolytic and photocatalytic splitting of H₂S

In this article, studies on the photolytic and photocatalytic splitting techniques for the generation of hydrogen from H₂S in aqueous and gas phase media under ultraviolet and/or visible light irradiation are reviewed. The kinetics of hydrogen production are also thoroughly discussed as a step towards process scale-up. Our findings indicate that the splitting of gaseous H₂S exhibits greater economic potential but shows much slower kinetics than its aqueous phase counterpart. Recent studies have demonstrated that higher efficiency can be attained with manganese sulfide (MnS) photocatalysts compared to cadmium sulfide (CdS), which in the past has been widely recognized as a promising photocatalyst for the production of H₂ from aqueous H₂S. Finally, the current challenges faced in implementing light-driven H₂S splitting and its prospects are highlighted. In particular, it was realized that future work needs to be directed towards the synthesis of novel photocatalysts or the development of reaction conditions that minimize or completely inhibit photo-corrosion, one of the major issues faced during the light-driven production of H₂ from H₂S in the presence of several photocatalysts. This critical review is envisaged to help fuel the renewed interest in the production of hydrogen through photocatalytic H₂S splitting.