TiO2-supported Ag nanoclusters with enhanced visible light activity for the photocatalytic removal of NO

Metal nanoparticles have been widely used in photocatalysis, while metal nanoclusters (NCs) smaller than 2 nm are barely studied for photocatalytic reactions. In this work, we explored the photocatalytic performances of the TiO2 supported Ag NCs (Ag NCs/TiO2). Interestingly, small loading amount (about 0.89% in Ag/Ti molar ratio) of Ag NCs on TiO2 (Ag NCs/TiO2-0.89) results in remarkable improvement in the photoactivity of NO removal. Ag NCs/TiO2-0.89 can remove 62% of NO in just 7 min, compared to that of only about 20% and 32% for the pristine TiO2 and Ag NCs, respectively. Besides, the support (TiO2) exhibits a strong effect, and Ag NCs/TiO2 0.89 is found to exhibit excellent stability and recyclability. More importantly, the composite can depress the amount of formed intermediate, NO2. In addition, Ag NCs/TiO2-0.89 has better photocatalytic performance against rhodamine B and methylene blue (cationic dyes) than methyl orange (anionic dye). This selectivity towards cationic dyes is interpreted by the electronegativity of AgNCs/TiO2-0.89 (the Zeta potential of which is 12.4 mV). Results also show that Ag NCs can behavior like a semiconductor, responding to the incident visiblelight, promoting the separation of photogenerated electron-hole pairs and producing center dot O2(-). Both center dot O-2(-) and photogenerated carriers are responsible for the photocatalytic reactions. The present study expands applications of Ag NCs, and highlights the vital effects of Ag NCs on the enhanced photoactivity and photocatalytic selectivity.