Reaction-atmosphere-driven dynamic metal dispersion enables self-optimizing Pt/θ-Al2O3 for efficient steam methane reforming

CO and steam drive the self-optimization of Pt/θ-Al 2 O 3 during SMR. • Surface Pt–CO species facilitate Pt redistribution into dispersed sites. • The dispersed Pt species enhance methane adsorption and activation under working conditions. • 0.1 wt% Pt gives >93% CH 4 conversion with near-unity H 2 selectivity at 700 °C. • Ce promotion suppresses long-term Pt sintering while preserving high activity. Maximizing noble-metal utilization under harsh reaction conditions remains a fundamental challenge in heterogeneous catalysis, as high temperatures typically drive irreversible metal sintering. Here, we report a reaction-atmosphere-driven dynamic dispersion mechanism that enables the in situ self-optimization of Pt/Al 2 O 3 catalysts during steam methane reforming (SMR). We show that the coexistence of steam and in situ generated CO promotes the progressive restructuring of Pt species toward highly dispersed, low-coordination metallic sites during activation. Spectroscopic analyses suggest that CO-containing intermediates may facilitate Pt restructuring through the formation of surface Pt–CO species, while steam induces the formation of surface hydroxyl groups on Al 2 O 3 that may help stabilize dispersed Pt species. This atmosphere-assisted restructuring process increases the number of accessible Pt surface sites during activation and improves Pt utilization under SMR conditions. As a result, an ultralow-loading Pt catalyst (0.1 wt%) achieves >93% CH 4 conversion with near-unity H 2 selectivity at 700 °C, together with an apparent TOF nearly an order of magnitude higher than that of higher-loading counterparts. Furthermore, moderate strengthening of metal-support interactions via Ce modification effectively suppresses long-term sintering without compromising activity. This work introduces a dynamic dispersion paradigm in which the reaction atmosphere actively governs catalyst structure under operating conditions, providing a general strategy for designing self-adaptive catalysts with maximized noble-metal efficiency in high-temperature reactions.