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Green Synthesis of Ag–TiO₂ Supported on Porous Glass with Enhanced Photocatalytic Performance for Oxidative Desulfurization and Removal of Dyes under Visible Light

Chen, Yuqing, Shen, Chun, Wang, Jie, Xiao, Gang, Luo, Guangsheng
ACS sustainable chemistry & engineering 2018 v.6 no.10 pp. 13276-13286
absorbance, adsorption, ambient temperature, catalysts, desulfurization, electrons, energy, energy conservation, glass, green chemistry, hydrogen, hydrogen peroxide, hydroxyl radicals, industrial applications, irradiation, light emitting diodes, methylene blue, oxidants, oxidation, oxygen, photocatalysis, rhodamines, silver, superoxide anion, viability
As the energy shortage and environmental problem become the worldwide concern, the green synthesis of catalysts and their green applications have long been pursued. Here we proposed a facile catalyst synthesis approach in which Ag–TiO₂ composites were prepared through an in situ reduction at room temperature without severe conditions or hydrogen atmosphere. Porous glass (PG) was chosen as the support, and the as-prepared Ag–TiO₂/PG was equipped with the remarkable merits of intense visible light absorbance, effective separation of electron–hole pairs, high surface areas for adsorption, and abundant reactive sites for the photocatalytic oxidation. Conversions of 95.2% and 92.1% for dibenzothiophene (DBT) and benzothiophene (BT), respectively, were realized under irradiation of energy-saving visible light emitting diodes (LEDs), complying with the principles of “green chemistry”. Moreover, none of the external oxidants, such as H₂O₂ or O₂, was introduced, greatly increasing the viability of industrial applications. Ag–TiO₂/PG also showed remarkable activity for removing rhodamine B (RhB), methylene blue (MB), and methylene orange (MO) with the rate constants of 0.14, 0.18, and 0.055 min–¹, respectively. The mechanism study revealed that the immobilized Ag acted as the role of “killing two birds with one stone”: enhancing the absorption of visible light, suppressing the recombination of photoinduced electron–hole pairs via trapping electrons, and contributing to the generation of •O₂–. In addition, oxygen vacancies, •OH, and h⁺ also took part in the photocatalytic oxidation. This work explored the green synthesis of Ag–TiO₂/PG and characterized their excellent photocatalytic activity for photocatalytic desulfurization and degradation of organic dyes, opening up new possibilities for low-energy-consumption photocatalysis and sustainable chemistry.