Incorporating Oxygen Atoms in a SnS<sub>2</sub> Atomic Layer to Simultaneously Stabilize Atomic Hydrogen and Accelerate the Generation of Hydroxyl Radicals for Water Decontamination
Shanpeng Li, Chunlei Liu, Wenying Lv, Guoguang Liu
Abstract
Photoelectrocatalysis (PEC) is an efficient way to address various pollutants. Surface-adsorbed atomic hydrogen (H*) and hydroxyl radicals (•OH) play a key role in the PEC process. However, the instability of H* and low production of •OH considerably limit the PEC efficiency. In this study, we noted that incorporating oxygen atoms could regulate the behavior of H* by creating a locally favorable electron-rich state of S atoms in the SnS2 catalyst. The finely modulated H* led to a 12-fold decrease in the overpotential of H2O2 generation (H*–OOH*–H2O2–•OH) by decreasing the activation energy barrier of OOH* (rate-determining step). Considering density functional theory calculations, an H*–•OH redox pair suitable for a wide pH range (3–11) was successfully constructed based on the photocathode. The optimal SnS1.85O0.15 AL@TNA photocathode exhibited a ∼90% reduction in Cr(VI) in 10 min and ∼70% TOC removal of 4-nitrophenol, nearly 2- and 3-fold higher than that without oxygen incorporation. Electron spin resonance spectrometry and radical quenching experiments verified that H* and the derived •OH via 1-electron and 3-electron reduction were the main active species. Operando Raman spectroscopy confirmed that the stable SnO2 phase helped constantly activate the production of H* and •OH.