Design\nStrategies for High-Performance NH<sub>3</sub>–SCO Catalysts:\nIdentifying and Modulating Direct Anchoring\nSites for Ag on TiO<sub>2</sub>

Ammonia\n(NH<sub>3</sub>) slip from diesel vehicle aftertreatment\nsystems and internal combustion engines fueled by NH<sub>3</sub> or\nNH<sub>3</sub>/H<sub>2</sub> poses serious environmental problems.\nAg-based catalysts are widely used for the selective catalytic oxidation\nof NH<sub>3</sub> to N<sub>2</sub> (NH<sub>3</sub>–SCO), and\ntheir performance is greatly dependent on the state of Ag, which is\ninfluenced by the anchoring sites on the support. Despite efforts\nto identify the direct anchoring sites of metal atoms on TiO<sub>2</sub>, conflicting views persist. Here, we compared the correlation between\nAg dispersion and the content of hydroxyl (OH) groups or defects on\nTiO<sub>2</sub> and conducted density functional theory (DFT) calculations,\nand the results confirmed that the surface OH groups of TiO<sub>2</sub> serve as the direct anchoring sites for Ag. By modulating the OH\ngroup content through thermal induction, the optimal OH group content\non TiO<sub>2</sub>-800 resulted in more metallic Ag nanoparticles\n(Ag<sup>0</sup> NPs) in larger sizes, leading to the development of\nan excellent NH<sub>3</sub>–SCO catalyst. Moreover, in situ\ndiffuse reflectance infrared Fourier transform spectroscopy (DRIFTS),\nkinetic studies, and DFT calculations suggested that more Ag<sup>0</sup> NPs in larger sizes on 10Ag/TiO<sub>2</sub>-800 were conducive to\nO<sub>2</sub> activation and NH<sub>3</sub> dissociation. Our findings\nprovide new insights for designing efficient NH<sub>3</sub>–SCO\ncatalysts, and OH groups as direct anchoring sites could be extended\nto other metals and supports for the rational design of catalysts.