Temperature‐programmed reduction of silver(I) oxide using a titania‐supported silver catalyst under a H₂ atmosphere

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.

Study of the Kinetics of Reduction of IrO2 on TiO2 (Anatase) by Temperature-Programmed Reduction

“…The qualitative partial agreement of the phase boundary and n-dimensional nucleation is in line with the expected phase and chemical transformation of IrO 2 to Ir metal. In the modeling, the deviation of n for the n-boundary controlled phase to 2.7 (Table 4) is in line with the expected 3D model (theoretically, n = 3 for a contracting sphere model) [44].…”

“…The qualitative partial agreement of the phase boundary and n-dimensional nucleation is in line with the expected phase and chemical transformation of IrO2 to Ir metal. In the modeling, the deviation of n for the n-boundary controlled phase to 2.7 (Table 4) is in line with the expected 3D model (theoretically, n = 3 for a contracting sphere model) [44]. It is common for reducible non-noble metal oxides such as Fe2O3 that multiple reduction regions occur [45,46], the first to Fe3O4 (that contains Fe 2+ and Fe 3+ ) and FeO (Fe 2+ )…”

Synergistic Effect in Ag/Fe–MnO2 Catalysts for Ethanol Oxidation

“…All samples are characterized by the wide peak of several components in H 2 -TPR profiles. Thus, for the Ag/OMS-2 sample, these are the maximum at 247 • C, attributed to the simultaneous reduction in manganese oxides [61], as well as two shoulders at temperatures of 170 and 350 • C. The low-temperature shoulder at 170 • C may also be due to the reduction in the adsorbed oxygen on the sample surface [62][63][64]. The shoulder at 350 • C may be due to the reduction in the manganese oxide that is not in contact with silver.…”

“…On the other hand, the authors of Ref. [64], who studied the reduction in Ag (1-10 wt.%)/TiO 2 catalysts, attributed the peak in the temperature range of 348-384 • C to the reduction in silver (I) oxide. In their opinion, additional reduction peaks can be due to the reduction in pore-deposited Ag 2 O, in which bulk lattice oxygen species experience a greater extent of the support interactions.…”

Sustainable energy technologies for the Global South: challenges and solutions toward achieving SDG 7

“…140,141 In such a context, it is necessary to develop novel ammonia synthesis or reductive catalysts. 142 These catalyst technologies are to be active under less severe operating conditions, appropriate to smaller-scale reactors, and could be practiced in the global south. By addressing its catalyst component, many of the problems associated with the process can be solved or could contribute to a greater solution.…”