Computational Insight into the Photocatalytic Splitting of H₂S during Gas-Solid Phase and Aqueous Phase Reactions

Hydrogen sulfide (H₂S) is a hazardous byproduct of industrial processes and poses significant environmental and health risks. Conventional methods for H₂S removal are not cost-effective, motivating the exploration of photocatalytic splitting of H₂S to both remove H₂S and generate hydrogen. Recent advancements in the use of graphitic carbon nitride materials (g-CN), consisting of heptazine units, have shown impressive progress in the photocatalytic splitting of H₂S. This study employs excited-state nonadiabatic dynamics simulations to investigate the molecular-level mechanisms of photoinduced H₂S splitting in both gas-solid and aqueous phases. Using a H₂S···heptazine model, the gas-solid phase reaction reveals an electron-driven proton transfer (EDPT) process as the key reaction pathway. In the aqueous phase, the photocatalyst significantly improves light absorption efficiency, as the H₂S···(H₂O)₄ cluster absorbs only a limited range of ultraviolet light. Moreover, the study demonstrates that the photoinduced holes transfer from the photocatalyst to H₂S and water molecules, which is a crucial step in enhancing the detachment of hydrogen atoms and their subsequent possible combination to form hydrogen gas. These findings provide valuable insights into the charge carrier dynamics and reaction mechanisms, elucidating the potential for efficient hydrogen production from the photocatalytic splitting of hazardous H₂S.