Rational regulation on charge spatial separation and directional migration in the yolk-shell structural SiO2/Ni2P/rGO/Cd0.5Zn0.5S nanoreactor for efficient photocatalytic H2 evolution

Abstract High-efficiency light utilization and prolonged lifetime of photo-induced charge carriers is a key step towards superior photocatalytic H2 evolution. Herein, the design of a novel spatially separated Ni2P co-catalyst decorated SiO2/rGO/Cd0.5Zn0.5S yolk-shell structural photocatalytic nanoreactor is reported. In this system, the advantages of ultrathin mesoporous shell and yolk-shell structure not only facilitate the mass diffusion with short length, but also allow broad-spectrum light absorption and increase the density of catalytic active sites. Importantly, the photo-generated electrons can be directionally injected from the outermost Cd0.5Zn0.5S shell to the spatially separated Ni2P co-catalyst. The dynamic behaviors of photo-induced charge carriers can be rationally regulated by the suitable energy level alignment and the built-in electric fields derived from both sides of embedded rGO interlayer. The synergistic effects of the excellent light-harvesting ability, more exposed active sites and improved charge separation efficiency significantly boosted the photocatalytic performances of hydrogen evolution. As a result, the optimal SiO2/Ni2P/rGO/Cd0.5Zn0.5S composite exhibited the highest hydrogen generation of 11.65 mmoL‧g-1‧h-1, even after five cycles. This work proposes new insights into the design of the efficient hollow sphere structural heterojunctions for photocatalytic water splitting applications.