Adaptive Restructuring toward Intrinsically Stable Rh Catalyst during Water-Gas Shift Reaction

Achieving intrinsic stability of reaction-formed catalytic sites, and understanding its origin, remains a central challenge in heterogeneous catalysis. Although CO-driven restructuring of atomically dispersed metals into subnanometer clusters has been observed in methane reforming and related reactions, the electronic basis of the resulting stability and the catalytic mechanism on these sites remain unknown. In this study, we show that atomically dispersed Rh on CeO₂ nanorods spontaneously evolves into Rh₃(CO)₄ clusters during the water-gas shift (WGS) reaction, and that this restructuring resolves the inherent activity-stability trade-off. Metastable Rh₃(CO)₃ clusters with higher initial activity transform into thermodynamically stable Rh₃(CO)₄ that sustains performance over 5000 h at 300°C without apparent deactivation. Combining in situ spectroscopy, kinetic analysis, and density functional theory calculations, we reveal the dual origins of this intrinsic stability. Coordination of the fourth CO ligand lowers the cluster formation energy by 2.15 eV, driven by $d_{z^2}$ -π* hybridization through Rh-to-CO back-donation, rendering Rh₃(CO)₄ a thermodynamic sink resilient to reaction-induced perturbations. Meanwhile, surface hydride species generated at oxygen vacancies open a concerted COOH dehydrogenation pathway, markedly lowering the rate-determining barrier. This work demonstrates that reactive atmospheres can steer catalytic sites toward configurations where structural stability and catalytic function coexist.