Artificial Photosynthetic Z-scheme Photocatalyst for Hydrogen Evolution with High Quantum Efficiency

As global energy consumption continues to rise, it is imperative to develop clean and renewable sources of energy as alternatives to the fossil fuel energy sources. Photocatalytic hydrogen generation or photochemical water splitting is a promising carbon-free technology producing H-2 and O-2 from water. Here, we report an exciting advance in the photocatalytic hydrogen evolution from water under visible light, using newly developed direct Z-scheme heterostructures constructed by oxygen deficient ZnO1-x nanorods and Zn0.2Cd0.8S nanoparticles by calcination. The highest rate for hydrogen production reaches 2518 mu mol h(-1) over optimal ZnO1-x (10 wt %)/Zn0.2Cd0.8S Z-scheme photocatalyst with a high apparent quantum efficiency (AQY) of 49.5% at 420 nm, which is 20 times higher than bare Zn0.2Cd0.8S and 25 times higher than ZnO1-x sample. From the results of photocurrent response, electrochemical impedance spectroscopy and time-resolved PL spectra, we demonstrate that the high increase in the photocatalytic hydrogen generation arises from the formation of artificial photosynthetic Z-scheme system and oxygen vacancy abundant ZnO1-x in the heterojunction. Direct Z-scheme ZnO1-x/Zn0.2Cd0.8S nanoheterostructures result in an efficient charge carrier separation and strong reduction ability for enhanced H-2 production; additionally, the presence of oxygen vacancies in the sample significantly enhances visible light absorption, these synergistic effects lead to highly efficient photocatalytic hydrogen production with an exceptional high quantum efficiency under visible light irradiation. Our findings provide possibilities for creating other high-efficiency photocatalysts mimicking natural photosynthetic Z-scheme system.