Reactivity of Titanium Oxide Clusters in C ₂ H ₄ Hydrogenation: Effects of Oxygen Deficiency, Cluster Size, and Pt Doping

ABSTRACT The catalytic hydrogenation of ethylene (C 2 H 4 ) on unsupported titanium oxide clusters (Ti x O y ) was investigated using density functional theory to examine the roles of oxygen deficiency, cluster size, and Pt doping. Oxygen‐deficient Ti 3 O 5 + generate localized centers that enhance H 2 activation and C═C hydrogenation, with Ti 3 O 5 + showing the lowest intrinsic barrier (2.09 eV). Reactivity improves with cluster size up to Ti 4 O 7 + and then saturates. Single‐atom Pt doping forms a bifunctional Pt–O interface that simplifies the mechanism and significantly lowers barriers. PtTi 3 O 5 follows a cooperative Pt–H/O–H pathway, while PtTi 4 O 7 exhibits a metal‐centered route with barriers as low as 0.60–0.81 eV. These results demonstrate that oxygen vacancies and Pt doping effectively tune Ti–O clusters toward noble‐metal‐like hydrogenation activity.