Abstract
Reduction kinetics of silver(I) oxide using a titania-supported silver catalyst was analyzed using temperature-programmed reduction (TPR) with hydrogen as a reducing gas. Ag2O reduction to Ag was observed in all samples as a single reduction step occurring at two reduction peaks. Observation of these reduction peaks indicates the existence of different lattice oxygen species, that is, surface and bulk, which are, respectively, attributed to surficial and pore-deposited Ag2O aggregates. The powdered samples exhibited high reducibility with average final oxidation states ranging from 0 to +0.18. The apparent activation energies for Ag2O reduction to Ag metal were 73.35 and 81.71 kJ/mol for surficial and pore-deposited Ag2O aggregates, respectively. In this study, a unimolecular decay model was reported to accurately describe the reduction mechanism of Ag/TiO2 catalysts. Hence, this would also infer that the catalyst reduction is rate-limited by the nucleation of Ag metal instead of the topochemical reaction and the diffusion of hydrogen and oxygen molecules.