Abstract: Effective separation of bulk phase and surface charges is crucial for maximizing charge utilization in the process of photocatalytic energy conversion. In this study, SnS₂ nanoflowers and twinned Mn_0.5Cd_0.5S solid solution (T-MCS) nanoparticles were fabricated by a one-step solvothermal method respectively, followed by the formation of SnS₂/T-MCS nanohybrids through a facile physical solvent evaporation process for high-efficiency photocatalytic hydrogen (H₂) production. The T-MCS crystal structure consists of alternating wurtzite Mn_0.5Cd_0.5S (WZ-MCS) and zinc blende Mn_0.5Cd_0.5S (ZB-MCS), forming a twin structure within the semiconductor. The charge migration mechanism between WZ-MCS and ZB-MCS follows the S-scheme pathway owing to slight differences in energy levels within their respective crystal structures, resulting in exceptional bulk phase charge separation capacity of T-MCS. Additionally, SnS₂ enhances the electrochemical performance of the catalysts by providing more active sites, reducing charge transfer resistance and H₂ production overpotential, thereby facilitating faster reaction kinetics. The photoelectrochemical tests, radical trapping experiments, density functional theory (DFT), and electron paramagnetic resonance spectroscopy (EPR) confirm that the charge transfer path between SnS₂ and T-MCS follows an S-type route that accelerates interfacial photo-induced electrons and holes separation while preserving useful charges. The synergistic impact of twinned homojunction and S-type heterojunction in 10 wt.% SnS₂/T-MCS composite contributes to a remarkable H₂ production rate of 182.82 mmol h^-1 g^-1, which is 761.8 times higher than that achieved with SnS₂ alone (0.24 mmol h^-1 g^-1), as well as 5.8 times higher than that achieved with T-MCS alone (31.54 mmol h^-1 g^-1). This study offers novel insights into designing highly efficient sulfide photocatalysts specifically targeting solar-driven H₂ evolution through a dual S-scheme transfer pathway.

Key words: Twinned Mn_0.5Cd_0.5S, SnS₂, Homo-heterojunctions, Double S-scheme, Photocatalytic H₂ evolution