Effect of Support on the Activity of Ag-based Catalysts for Formaldehyde Oxidation

Abstract

Ag-based catalysts with different supports (TiO2, Al2O3 and CeO2) were prepared by impregnation method and subsequently tested for the catalytic oxidation of formaldehyde (HCHO) at low temperature. The Ag/TiO2 catalyst showed the distinctive catalytic performance, achieving the complete HCHO conversion at around 95 °C. In contrast, the Ag/Al2O3 and Ag/CeO2 catalysts displayed much lower activity and the 100% conversion was reached at 110 °C and higher than 125 °C, respectively. The Ag-based catalysts were next characterized by several methods. The characterization results revealed that supports have the dramatic influence on the Ag particle sizes and dispersion. Kinetic tests showed that the Ag based catalyst on the TiO2, Al2O3 or CeO2 supports have the similar apparent activation energy of 65 kJ mol−1, indicating that the catalytic mechanism keep immutability over these three catalysts. Therefore, Ag particle size and dispersion was confirmed to be the main factor affecting the catalytic performance for HCHO oxidation. The Ag/TiO2 catalyst has the highest Ag dispersion and the smallest Ag particle size, accordingly presenting the best catalytic performance for HCHO oxidation.

Catalytic Hydrogen Production by Janus CuAg Nanostructures

“…Cu NPs/ZnO and Ag NPs/ZnO were also investigated for comparison . As shown in Figure a, the Ag 3d binding energies of these three Cu−Ag NPs/ZnO are approximately 367.9 eV and 373.7 eV (corresponding to Ag 0 ), while those of Ag NPs/ZnO are 367.3 eV and 373.3 eV (corresponding to Ag + ),, suggesting that the Ag species in these three Cu−Ag NPs/ZnO had an enhanced antioxidant capacity compared with Ag NPs/ZnO. More interesting, we found the similar results in the Cu 2p signals (Figure b).…”

Antimicrobial dependence of silver nanoparticles on surface plasmon resonance bands against <em>Escherichia coli</em>

“…Zhang et al39 reported that during the formation of AgNPs in the solution, there is biodegradation of HCHO to HCOO − via silver oxidation catalytic activity 40,41…”

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

“…Hence, the classical view of metal particles remaining electronically unperturbed on a metal oxide support would not be the entirely accurate concept for the Ag/TiO 2 catalyst. The partial reduction of TiO 2 was also reported using Ag/TiO 2 catalysts synthesized by Zhang et al for formaldehyde oxidation. For bare titania support, they observed the onset of this phenomenon at 822 K, which is higher than that reported in this study (657 K).…”

“…Both peaks were attributed to Ag 2 O reduction by catalysts as both peaks were not observed in TiO 2 patterns. The first peak would be reduction of Ag 2 O particles to Ag as commonly reported to occur within the temperature range of 353–423 K . As for the additional Ag 2 O reduction at higher temperature, there are two plausible reasons to this phenomenon: (a) Variation in particle size of TiO 2 or Ag 2 O species; (b) Reduction variation between surface and bulk lattice oxygen species.…”

“…Nevertheless, both studies observed the effect of Ag metal in facilitating partial TiO 2 reduction as evidenced by the decrease in TiO 2 reduction peak temperature upon Ag addition. Another issue to be considered would also be formation of oxygen vacant sites upon reduction of TiO 2 as according to the following reactions: where is the oxygen vacant site. These generated oxygen vacancies were also reported by Khader et al to favor further H 2 adsorption, which would be beneficial for activation and adsorption of hydrogen.…”