An ultrafast H* migration channel and oxidation activity driven by multifunctional Co atoms on twin Co0.01Mn0.29Cd0.7S homojunction surface for photocatalytic overall water splitting

Low kinetics of water dissociation, unfavorable hydrogen adsorption, and high water-oxidation barriers restrict the photocatalytic overall water splitting (OWS) efficiency over sulfides. Herein, multifunctional Co atoms are doped on the twin Mn0.3Cd0.7S homojunction surface for efficient photocatalytic hydrogen (H2) and oxygen (O2) evolution. An ultrafast hydrogen atom (H*) migration channel bridging the water dissociation/H2 evolution step is established between cubic-S and hexagonal-S sites by introducing Co atoms, facilitating the HER kinetics. Specifically, Co atoms regulate the electron properties of neighboring S atoms and weaken their charge accumulation, which promotes cubic-S sites to capture sufficient H* from the water dissociation zone and accelerates hexagonal-S sites to release H2 through the H* migration channel. Meanwhile, unsaturated Co atoms on the cubic phase as oxygen evolution reaction (OER) sites promote water deprotonation and optimize the kinetics of the rate-determining step to form OOH* intermediate, enhancing water oxidation activity. Co atoms strengthen the internal electric field of the homojunction and local polarized electric field by increasing the work function difference between the two phases and introducing the high spin polarization, inhibiting the bulk and surface recombination of photogenerated carriers. The Co0.01Mn0.29Cd0.7S exhibits visible-light-driven H2 and O2 evolution rates of 443.12 and 219.67 μmol g−1 h−1, about 50 times that of the Mn0.3Cd0.7S. This work provides some guidance for the design of homojunction photocatalysts with efficient OWS performance.