Modulating lattice-oxygen-mediated redox properties and catalytic activity of TiO2 nanoparticles via atomic substitution

Developing noble-metal-free oxidation catalysts that operate efficiently under mild conditions remains a central challenge. Here, we present an atomic substitution strategy for anatase TiO 2 nanoparticles, using 3 d transition metals (Cr to Ni) to alter lattice‑oxygen redox properties and CO oxidation kinetics. The catalyst series exhibits a volcano-type activity profile, peaking at Co-TiO 2 , which affords 10 5 -fold higher specific reaction rate and achieves complete CO conversion at temperatures up to 350 °C lower than those of TiO 2 . This enhancement arises from a 45 kJ mol −1 reduction of the activation barrier. Transient CO–O 2 cycling and theoretical modeling together attribute this optimum to rapid lattice‑oxygen activation sustained without excessive vacancy accumulation in the classical Mars–van Krevelen regime. In contrast, Ni-TiO 2 , which is anomalously less active despite its superior reducibility, follows a vacancy-pair-mediated reoxidation sequence. This kinetic divergence drives dynamic surface reconstruction, leading to initially low activity that gradually recovers during redox cycling. These insights show that, beyond tuning adsorption–activation trade-offs, the precise control of steady-state vacancy population constitutes a new design principle for redox-tunable oxide catalysts.