Dodecylamine coordinated tri-arm CdS nanorod wrapped in intermittent ZnS shell for greatly improved photocatalytic H₂ evolution

A new photocatalyst, the tri-arm CdS/ZnS core–shell nanorod, is carefully designed for the first time, where tri-arm CdS nanorods are decorated by dodecylamine (DDA) molecules and then wrapped in an intermittent ZnS shell. The resultant photocatalyst with a CdS/ZnS mole ratio of 0.5 (CZS_0.5) presents a significantly improved H₂ evolution rate of 726.0 μmol/h (3 mg of catalysts, equal to 242.0 mmol/g/h) in the absence of co-catalysts, which is currently the highest value in CdS-based catalysts. The apparent quantum efficiency of CZS_0.5 reaches 50.61% at 380 nm. The significantly enhanced photocatalytic performance can be attributed to a win–win situation between the analogous type-II mechanism formed in the CdS/ZnS heterojunction and the H⁺ adsorption resulting from the DDA molecules. Due to the analogous type-II mechanism, photogenerated electrons are transferred from the ZnS shell to the CdS nanorod. Owing to the decoration of DDA, many H⁺ ions are adsorbed on CdS. Thus, the photogenerated electrons gathered in CdS can be captured quickly and in a timely manner by the adsorbed proton H⁺ to produce hydrogen, which effectively suppresses the recombination of photogenerated electrons and holes. This study may bring new insights for developing other photocatalysts with high performance by using small organic molecules.