Synthesis of visible-light-responsive YbTaO4-xNy via work-function difference metal assistance nitridation for photocatalytic overall water splitting

Abstract

Tantalum-based oxynitrides have garnered intensive attention in photocatalytic water splitting due to their suitable band structures. Nevertheless, their nitridation process typically requires high temperatures (≥ 1123 K). Reducing the nitridation temperature inevitably results in nitrogen deficiency, which restricts the visible-light absorption range. Leveraging the metal-assisted nitridation strategy developed by our group previously, we herein investigated the promotional effect of metals with different work functions on the low-temperature (923 K) nitridation process. A series of YbTaO_4-xN_y(M) (M = Mg, Zr, Al) oxynitrides were successfully fabricated. It revealed that the nitrogen content increases with decreasing work function of the nitridation-assisting metals. Nitrogen doping effectively red-shifted the optical absorption edge of the sample from the ultraviolet to the visible light region. After modifying YbTaO4-xNy(Mg) or YbTaO4-xNy(Zr) with Pt@CrOx and IrO₂ dual co-catalysts, stoichiometric H₂ and O₂ evolution was achieved under visible-light irradiation (λ ≥ 420 nm) in pure water without any sacrificial agents. This work clarifies the intrinsic correlation between the work function of nitridation-assisting metals, nitridation doping content, and photocatalytic activity, providing a scalable experimental protocol for the rational design of high-performance visible-light-responsive tantalum-based oxynitrides.