Ag/Bi2MoO6-x with enhanced visible-light-responsive photocatalytic activities via the synergistic effect of surface oxygen vacancies and surface plasmon

Abstract

In this study, a heterostructured Ag/Bi2MoO6-x photocatalyst was rationally designed and successfully fabricated via the deposition of plasmonic silver nanoparticles onto the surface of Bi2MoO6 with surface oxygen vacancy (denoted as Bi2MoO6−x). Bi2MoO6−x (Abbr. BMO6-x was first synthesized via a solvothermal synthesis and calcination process. The plasmonic silver nanoparticles were then loaded onto the surface of BMO6−x using a simple photoreduction process to form Ag/BMO6−x composite. Surface oxygen vacancies (SOVs) in BMO6−x were confirmed by electron paramagnetic resonance (EPR) spectrum. The structures of BMO6−xand Ag/BiMoO6−x) were characterized using high-resolution transmission electron microscopy, powder X-ray diffraction, and X-ray photoelectron spectroscopy. Under visible light irradiation, sample Ag/BMO6−x exhibits a highest visible-light-responsive photocatalytic performance compared to those of pure-Bi2MoO6 (BMO), BMO6−x and Ag/BMO for the degradation of rhodamine B (RhB), which is attributed predominantly to the synergistic effect of SOVs and Ag surface plasmonic resonance (SPR) on the surface of Bi2MoO6−x leading to the efficient separation and migration of photogenerated electrons/holes and hence broadening light responsive region. The significant improvement of the migration and separation of photogenerated electrons/holes in the Ag/BMO6−x was evidenced by photoluminescence spectra, time-resolved fluorescence decay, photocurrent, and electrochemical impedance spectrum. The ESR with spin-trap technique and reactive species trapping experiments confirm that the mainly active species O2− and h+ are playing key roles in the RhB photodegradation process over Ag/BMO6−x. This study not only provides an understandable synergistic effect of SOVs and SPR Ag but also pioneers a new approach for fabricating a series of highly catalytically active metal-semiconductor photocatalysts with surface atom defects.