Deliberate construction of direct Z-scheme photocatalysts through photodeposition

Abstract

Constructing Z-scheme type photocatalysts is preferred to achieve efficient photocatalyst owing to the high oxidative and reductive capabilities of composite catalysts. The direct Z-scheme (DZS) is composed of two semiconductors contacting each other, which eliminates the disadvantages of using an electron mediator in liquid and solid-state Z-schemes. However, deliberately constructing a DZS remains challenging. In this report, two semiconductors were denoted as SC-I and SC-II according to the natural photosynthesis process. Two routes for constructing DZS catalysts through photodeposition were demonstrated, which effectively regulated the photogenerated charge transfer direction. Starting from SC-I, SC-II was selectively deposited at the hole-rich site of SC-I by photooxidation. Starting from SC-II, SC-I was selectively grown at the electron-rich site of SC-II through photoreduction. This selective deposition promoted directional charge recombination to form DZS catalysts. Two examples, Fe₂O₃/g-C₃N₄ and CdS/TiO₂, were synthesized by photooxidation and photoreduction, respectively. Charge-transfer tracking and reactive oxygen species were used to check the charge transfer direction and radical type. The results showed that both systems indeed formed DZS catalysts. Based on the above results, photodeposition can be used to deliberately construct DZS catalysts.