A comparison of dry and wet condition CO oxidation activity of a supported silver catalyst at low temperature

Abstract

The rational design of a highly efficient and sustainable strategy to remove CO by oxidation at low temperature is extremely desirable and increasingly important to control air pollution, interconnected to human health. However, the development of an efficient and cost-saving catalyst confronts challenges to activity and stability. Here, we developed a series of less expensive Ag catalysts supported on industrially relevant TiO₂ and systematically investigated the CO oxidation activity after the characterization of the catalyst using various techniques. First, morphological analyses suggested the presence of spherical Ag particles dispersed on crystalline TiO₂, and spectroscopic studies confirmed the existence of the Ag-oxide species. Furthermore, the Ag/TiO₂ catalyst displayed remarkable CO oxidation activity without any oxidation–reduction pretreatment or surface modifications (a general trend to improve the catalytic efficiency). Notably, 3 wt% Ag/TiO₂ completely converted CO at 80 °C (T_50% = 34.6 °C) with high productivity and a turnover frequency of 1.4 μmol_CO⁻¹ g_Ag⁻¹ s⁻¹ and 5.2 × 10⁻⁴ s⁻¹ at 20 °C, respectively. Interestingly, Ag/TiO₂ retained its excellent catalytic performance even in the presence of water, which significantly enhanced its stability. Moreover, the effect of different support materials was also investigated. Finally, a correlation between the catalytic activity and structural characterization was derived via multi-technique analyses, which illustrated that the remarkable activity and high stability of the catalyst are reliant on the synergistic contribution of active reducible Ag-oxide species and the support material at the metal–support interface.