New insights into how RGO influences the photocatalytic performance of BiOIO₃/RGO nanocomposites under visible and UV irradiation

Reduced graphene oxide (RGO) has been demonstrated to be effective in enhancing the photocatalytic activity of various semiconductors. However, an important issue that has been overlooked is the role of RGO in UV-induced photocatalysis of RGO-based nanocomposites. In the present work, novel BiOIO₃/RGO nanocomposites were prepared by a simple one-pot hydrothermal method, during which BiOIO₃ nanoplates were formed in situ on RGO sheets resulting from partial reduction of RGO. The two components of the composite displayed intimate interfacial contact. The as-prepared BiOIO₃/RGO nanocomposites exhibited highly enhanced visible photocatalytic activity, relative to that of pure BiOIO₃, toward removal of NO from air. However, the BiOIO₃/RGO nanocomposites showed only slightly increased photocatalytic activity, relative to pure, under UV irradiation. The limited enhancement of UV activity can be ascribed to the fact that BiOIO₃ would be expected to compete with RGO with regard to absorption and utilization of UV light. Evidence shows that RGO can act as a semiconductor rather than a photosensitizer or electron reservoir in BiOIO₃/RGO nano-composites. In addition, the active species responsible for photoactivity have been investigated by a DMPO spin-trapping electron spin resonance technique. Photo-generated holes were found to be the main active species inducing the photo-oxidation of NO under visible light, whereas holes and OH radicals are considered to be responsible for photo-activity under UV light. This work points to BiOIO₃/RGO nano-composites as new and efficient visible light photocatalysts for environmental remediation applications, and also as a source of new insights into the pivotal role of RGO in photocatalysis of RGO-based nanocomposites under visible as well as UV light. Copyright © 2015 Elsevier Inc. All rights reserved.