Modulated Structure‐Electronic Coupling at Pt/CeO x –TiO ₂ Interfaces Boosts Low‐Temperature Preferential CO Oxidation

Preferential oxidation, PROX, of residual CO in a hydrogen‐rich synthetic gas is the final stage of industrial hydrogen production and purification. However, selectively oxidizing around 1 vol. % of CO without consuming hydrogen is technically challenging. Here, we use Pt single atoms (SAs) stabilized on CeO x –TiO 2 supporting oxides toward PROX of CO. Based on a combined study of density functional theory calculations and in situ spectroscopic analyses, we identified the delicate electronic states of the reaction centers. The bifunctional nature of the spatially separated Pt–O–Ti and Pt–O–Ce sites promoted selective PROX of CO. The preferentially adsorbed hydrogen at the Pt–O–Ti site behaves as an activity regulator, donating electrons to Pt, thus reducing Pt–SAs. The oxygen ion at the Pt–O–Ce interface actively oxidizes the weakly adsorbed CO on reduced Pt–SAs. The unique structural and electronic ensembles at the Pt–CeO x –TiO 2 interfaces suppress hydrogen consumption but, instead, promote the PROX of CO under hydrogen‐rich conditions with high specific mass activity and 100 % selectivity for CO 2 at below 100°C. We present a representative case of using electronic modulation of Pt–SAs under reaction conditions, enabled by the unique structural ensemble of Pt‐oxide interfaces, to activate Pt–SAs dynamically.