Engineering Cationic Sulfur-Doped Co₃O₄ Architectures with Exposing High-Reactive (112) Facets for Photoelectrocatalytic Water Purification

Promoting the generation of intermediate active species (superoxide radical (^•O₂^–)) is an important and challenging task for water purification by photoelectrocatalytic (PEC) oxidation. Herein, we have constructed hierarchical cationic sulfur-doped Co₃O₄ architectures with controllable morphology and highly exposed reactive facets by introducing l-cysteine as a capping reagent and sulfur resource via a one-step hydrothermal reaction. The as-obtained cationic sulfur (1.8 mmol l-cysteine) source doped Co₃O₄ (SC-1.8) architectures with highly exposed (112) facets exhibited superior PEC activities and long-term stability (∼25,000 s) in 1.0 mol·L^–1 sulfuric acid for an accelerated reactive brilliant blue KN-R degradation test. Our experimental and theoretical results confirmed that the superior PEC performance of the SC-1.8 architectures could be ascribed the following factors: (1) the highly exposed reactive (112) facets of SC-1.8 promoted carrier transport and diffusion during the PEC process and facilitated separating the electron/hole pairs and producing the predominant active species (^•O₂^–) compared with currently used other electrodes. (2) Cationic sulfur doped on the lattice of Co₃O₄ can narrow the band gap to extend the photoadsorption range and improve the lifetime of ^•O₂^– to enhance the PEC efficiency. This work not only proves that the SC-1.8 architectures with highly exposed (112) facets are a promising PEC catalyst due to increasing the electron transport and the lifetime of active species but also presents a new strategy for constructing an active PEC catalyst.