Constructive Transformation of WS ₂ into Atomically Dispersed W−O Sites Enables Stable Photocatalysis

High Resolution Image Download MS PowerPoint Slide Single-layer transition metal dichalcogenides (TMDs), such as WS 2, offer promising catalytic performance and good electron mobility, making them attractive cocatalysts for photo- and electrocatalysis. However, their structural instability under reaction conditions often leads to formation of inactive bulk metal oxides and contamination of final products, limiting long-term performance and industrial applicability. Herein, we demonstrate that this instability can instead be harnessed as a constructive transformation pathway. Under mild aqueous conditions, exfoliated WS 2 monolayers undergo spontaneous transformation at the interface with anatase TiO 2, resulting in the formation of highly dispersed tungsten species anchored on the oxide surface and accompanied by the generation of abundant oxygen vacancies. Comprehensive structural, spectroscopic, and theoretical analyses reveal that strong interfacial interactions direct the oxidation pathway away from bulk oxide formation and toward stabilized, atomically dispersed active sites with modified local electronic structures. The resulting catalyst exhibits enhanced charge separation, improved conductivity, and markedly improved stability and performance under photocatalytic conditions. These serendipitous findings reframe TMD degradation as a beneficial process and establish a strategy for repurposing unstable metal sulfide monolayers into functional components of robust photocatalytic systems.