Visible light-driven dehydrocoupling of thiols to disulfides and H2 evolution over PdS-decorated ZnIn2S4 composites

The simultaneous utilization of photogenerated electrons and holes in one cooperative photoredox system for the dehydrocoupling of thiols into value-added disulfides and clean hydrogen (H2) fuel meets the development criteria of green chemistry. Herein, we report the synthesis and application of cocatalyst PdS decorated ZnIn2S4 (PdS-ZIS) composites for photocatalytic coupling of thiols into disulfides and H2 evolution under visible light irradiation. The superior photocatalytic performance over PdS-ZIS composites compared with blank ZIS is attributed to the function of PdS as oxidation cocatalyst, which dramatically promotes the separation and transfer of photogenerated charge carriers due to its excellent hole trapping ability. In-situ Fourier transform infrared spectra reveal the dynamic variation of reactants on the catalyst surface. Electron paramagnetic resonance technology confirms that sulfur-centered radicals are the key reaction intermediates in this coupling process. Moreover, the application of PdS-ZIS composites to the dehydrocoupling of various thiols with different substituent groups into the corresponding S–S coupling products has been demonstrated to be practicable. This work is expected to offer insights into the rational design of cocatalyst-decorated semiconductor photocatalysts with efficient utilization of photogenerated electrons and holes for the co-production of high-value chemicals and clean H2 energy in a cooperative photoredox catalysis process.