Modulating the anchoring states of Ag on TiO2 by SiO2 to boost the NH3-SCO activity over Ag-based catalysts

Abstract

Ag-based catalysts show high activity in NH3-selective catalytic oxidation (NH3-SCO). The anchoring states of Ag species determines its valence and dispersion, thereby influencing the performance of Ag-based catalysts. Herein, we elucidated that the content and anchoring strength of the hydroxyl (OH) groups on support together affect the anchoring states of Ag. TiO2 has few OH groups but high anchoring strength, the anchored Ag is in a highly dispersed oxidized state, while the unanchored Ag is aggregated in a metallic state (Ag0), so it presents an unevenly sized dispersion and mainly in oxidized state. SiO2 has abundant OH groups but weak anchoring, and can excessively agglomerate into large Ag0 nanoparticles (Ag0 NPs). Therefore, the introduction of SiO2 can regulate the anchoring states of Ag on the TiO2 support, making Ag presents highly dispersed Ag0 NPs, thus following a reaction mechanism with lower energy barriers and significantly improving the NH3-SCO performance.