Photocatalysis in an evanescent field: an in situ approach to studying photocatalytic performance by tracing interfacial refractive index changes and kinetics

Abstract

An in situ strategy to understand the photocatalytic performance of Cu₂O–Ag@rGO nanocomposites through interfacial photocatalysis on an optical microfiber has been proposed and experimentally demonstrated. The photocatalysts were conjugated on the surface of an optical microfiber immersed in an organic solution, forming an interface consisting of photocatalysts and organic molecules between the silica microfiber and the solution, which was within the evanescent field of the optical microfiber. In the photocatalytic process, the decomposition of organics changed the refractive index (RI) of the interface. The interaction between the evanescent wave and the microfiber interface modulated its optical spectrum. Therefore, the optical microfiber monitored the photocatalytic performance of the photocatalysts in real-time and in situ. The results reveal that the photodegradation efficiency of Cu₂O–Ag@rGO was almost twice that of Cu₂O, while the degradation rate constant was more than five times larger, because the coupling between the silver nanoparticles and reduced graphene oxide (rGO) enhanced the photocatalytic performance of Cu₂O. By taking advantage of its miniature size and mechanical flexibility, the microfiber can directly probe a real matrix to study the local photocatalytic performance. This strategy is suitable for the evaluation of most photocatalysts and might provide a new perspective to assess the photocatalytic performance of the catalysts.