Intrinsic Necessity of the Reduced Catalyst for CO Oxidation: Stable Pt Clusters Rather Than Unsustainable Oxygen Vacancies

H2 treatment induces a distinct strong metal−support interaction (SMSI) on the Pt/TiO2 catalyst surface, generating highly stable Pt nanoclusters (Pt-NCs) and abundant oxygen vacancies (Ov), which significantly increase the CO oxidation activity. In this study, a 0.1Pt/Ti catalyst was initially subjected to H2 pretreatment and then exposed to air to obtain the 0.1Pt/Ti-H2-Air catalyst. Compared with the untreated 0.1Pt/Ti catalyst, both the 0.1Pt/Ti-H2 and 0.1Pt/Ti-H2-Air variants exhibited enhanced performance in the catalytic oxidation of CO. Notably, the TOF of 0.1Pt/Ti-H2 reached 3.87 s−1, representing a 97-fold increase over that of the untreated catalyst (TOF = 0.04 s−1), whereas the TOF of 0.1Pt/Ti-H2-Air was reduced to 0.21 s−1, reflecting the gradual consumption of Ov during the reaction. A comprehensive characterization revealed that the synergistic interaction between the Pt-NCs and oxygen vacancies facilitated the catalytic oxidation process. As the reaction proceeds, the number of oxygen vacancies gradually decreases, yet the Pt-NCs remain structurally stable and continue to play a pivotal role-underscoring the importance of reductive pretreatment in sustaining high catalytic activity under oxidizing conditions.