Boosting visible-light-driven photocatalytic H2 production by optimizing surface hydrogen desorption of NiS/CdS–P photocatalyst

Abstract

Metal chalcogenides are regarded as favorable H2-evolution cocatalysts; however, they often exhibit unfavorable H desorption characteristics due to the strong affinity of nascent H and highly electronegative S sites, which significantly inhibit H2 generation. To address this issue, a general approach to electron-enriched control of sulfur-active sites is developed for weakening the strong interaction of S–H bonds. This is achieved through the formation of a nanostructured model composed of NiS/CdS–P, in which the surface phosphorus (P) atoms are incorporated in CdS NRs to create an imbalanced charge distribution and a localized built-in electric field in the crystal structure of CdS. In this situation, the built-in electric field not only separates the photogenerated electron hole pairs, but it also accelerates the photogenerated electrons from the CdS–P conduction band to the NiS surface for rapid hydrogen reduction rather than hydrogen adsorption. Photocatalytic tests show that the resultant NiS/CdS–P photocatalyst displays a significant H2-generation rate of 44.39 mmol g−1 h−1 and an apparent quantum efficiency of 41% at 420 nm. Valance band XPS analysis shows that CdS–P has a higher electron density than CdS, leading to the production of electron-rich Sδ− active centers. This better photocatalytic hydrogen generation might be due to the synergistic impact of tailoring the intrinsic built-in electric field for the acceleration of photogenerated charges by P-doping and the fabrication of a NiS cocatalyst for hydrogen reduction rather than hydrogen adsorption. The concept of optimizing the electron densities of active sites by morphology tailoring, with an extra built-in electric field, gives a method for rationally constructing artificial photocatalysts for solar power conversion.