Silver Oxide as Superb and Stable Photocatalyst under Visible and Near-Infrared Light Irradiation and Its Photocatalytic Mechanism

Photocatalytic processes are an environmentally friendly technology for treatment of persistent organic pollutants. However, the majority of current photocatalysts cannot utilize sunlight sufficiently to realize fast decomposition of organic pollutants. In this research, a silver oxide nanoparticle aggregation with superb photocatalytic performance under artificial light source and sunlight was prepared and characterized. The results showed that methyl orange (MO) was decomposed completely in 120 s under irradiation of artificial visible light, artificial ultraviolet light, and sunlight, and in 40 min under near-infrared (NIR) light. The superb photocatalytic performance of as-prepared silver oxide remained almost constant after reuse or exposure under sunlight. It was confirmed that the co-working effect of photogenerated hole and ozone anion radicals did play an important role in the process of MO photodegradation with the existence of Ag₂O. The narrow band gap of Ag₂O, less than 1.3 eV, resulted in the photocatalytic performance of Ag₂O under NIR light. Furthermore, the high surface area and numerous crystal boundaries provided by the aggregation of Ag₂O nanoparticles efficiently increased the escape probability of photogenerated electrons and the contact probability of photogenerated holes with outside materials, assuring superb photocatalytic activity and excellent stability of as-prepared Ag₂O samples.