Twin Zn_{1- x} Cd_x S Solid Solution: Highly Efficient Photocatalyst for Water Splitting

Twins in crystal defect, one of the significant factors affecting the physicochemical properties of semiconductor materials, are applied in catalytic conversion. Among the catalysts serving for photocatalytic water splitting, Zn_{1- x} Cd_x S has become a hot-point due to its adjustable energy band structure. Via limiting mass transport to control the release rate of anions/cations, twin Zn_{1- x} Cd_x S solid solution is prepared successfully, which lays a foundation for the construction of other twin crystals in the future. On twin Zn_{1- x} Cd_x S, water tends to be dissociated after being adsorbed by Zn²⁺ /Cd²⁺ at twin boundary, then the fast-moving electrons at twin boundary quickly combine with the protons already attached to S^2- to form hydrogen. According to the theoretical calculation, not only the intracrystalline electron mobility, but also the extracrystalline capacity of water-adsorption/dissociation and proton-adsorption on the twin boundary are superior to those of the counterpart plane in defect-free phase. The synthetic twin Zn_{1- x} Cd_x S apparent quantum efficiency of photocatalysis water splitting for hydrogen reached 82.5% (λ = 420 nm). This research opens up an avenue to introduce twins in crystals and it hopes to shed some light on photocatalysis.