Defect-Engineered Alumina Stabilizes Metallic Platinum Nanoclusters for Interfacial O2 Activation in Oxidation Catalysis

Controlling oxide support electronics provides direct access to the state and reactivity of supported noble metal catalysts via interfacial O2 activation. Here, defect-rich alumina (Al2O3–x), generated by pyrolysis of basic aluminum acetate hydroxide, stabilizes ultrafine metallic Pt nanoclusters without a separate reduction step, whereas commercial Pt/Al2O3 mainly forms oxidized Pt species and larger particles. The defective alumina contains abundant unpaired electrons and oxygen vacancy-related electronic defect states, which are believed to contribute to the stabilization of metallic Pt nanoclusters. Pt/Al2O3–x therefore shows enhanced low-temperature activity relative to Pt/Al2O3 in CO, C3H6, and NH3 oxidations. CO oxidation identifies the origin of this enhancement: the Pt/Al2O3–x interface facilitates O2 activation through a stronger Pt–O interaction and weakened O–O bonding in adsorbed oxygen species, lowering the barrier for oxidative turnover. The defect-rich nature of Al2O3–x is closely associated with the stabilization of metallic Pt nanoclusters and enhanced interfacial O2 activation, which together contribute to the superior oxidation performance. These findings establish defect-rich support environments as a key handle for stabilizing metallic Pt nanoclusters and controlling interfacial O2 activation, offering a general design principle for robust oxidation catalysts.