Perimeter Power: Unveiling the Role of Ni-TiO2 Interface Sites in Enhancing Acetic Acid Ketonization Catalysis

Catalytic ketonization of biomass-derived carboxylic acids is a key step in upgrad- ing oxygenates, yet achieving high rates with stability on oxides remains challenging. We show that highly dispersed Ni on TiO2 creates Ni–Ti perimeter sites that markedly enhance acetic acid ketonization. A 0.25 wt% Ni/TiO2 catalyst exhibits a 2.3-fold higher turnover frequency than TiO2 at 623 K, while sustaining activity. XRD and TEM reveal no detectable Ni crystallites and CO chemisorption indicates high dispersion; in situ DRIFTS resolves distinct interfacial binding modes. Density functional theory attributes the rate enhancement to lowered barriers for α-C–H activation at Ni–Ti perimeters (0.72 eV) relative to pristine TiO2 (1.10 eV), consistent with kinetics showing accelerated rates and reduced deactivation. Activity displays a volcano-type dependence on Ni loading, reflecting a bifunctional adsorption synergy in which carbonyls bind at the Ni–TiO2 interface while methyl fragments coordinate to metallic Ni. The resulting perimeter environment stabilizes α-hydroxy enolate intermediates that drive efficient C–C coupling to ketone products. These findings establish perimeter engineered Ni/TiO2 as an effective platform for acetic-acid ketonization and provide design principles for robust catalysts that couple oxygenates under thermochemical conditions