Fluorine Passivated Perovskite SrNbO2N Photocatalyst for Robust Sunlight-Driven Water Splitting

Abstract

SrNbO₂N is a promising narrow-bandgap semiconductor for sunlight-driven water splitting but is generally subject to insufficient photocarrier separation and severe photocorrosion. Here, the targeted single-crystalline SrNbO₂N nanobelts are passivated by consecutive annealing in O₂ and N₂/NH₄F to approach the right N/O ratio (1/2) and anion content (O + N = 60 at%). The passivation measures lead to both a low concentration (≈2.2 × 10¹⁵ cm⁻³) of defects including V_O, Nb³⁺, Nb⁴⁺ for efficient photocarrier separation and unique fluorine-rich, nitrogen-poor surface with low surface energy for high stability against photocorrosion. Notably, the passivated SrNbO₂N nanobelts deliver the highest values of photocurrent density of 4.5 mA cm⁻² at 1.23 V versus RHE and stable photocatalytic (PC) Z-scheme overall water splitting activity of ≈10 µmol h⁻¹ H₂ evolution under AM 1.5G illumination when used as photoanode materials for photoelectrochemical (PEC) water oxidation and the photocatalytic O₂-evolution moiety, respectively. These findings provide not only an effective guideline to upgrade the activity and stability of SrNbO₂N but also fresh mechanistic insights into the role of passivation measures.