Reduced graphene oxide modified Z-scheme AgI/Bi2MoO6 heterojunctions with boosted photocatalytic activity for water treatment originated from the efficient charge pairs partition and migration.

Abstract

In order to enhance degradation of harmful organic pollutants like Rhodamine B (RhB) dye under visible-light irradiation (λ >420 nm), a silver iodide/reduced graphene oxide/bismuth molybdate (AgI/rGO/Bi2MoO6) Z-scheme heterojunction photocatalyst was synthesized by a solvothermal process combined with an in-situ precipitation technique. The AgI (15 wt.%)/rGO/Bi2MoO6 (AGBMO-15) photocatalyst with a dosage of 0.5 g/L exhibited the highest photocatalytic activity with 98.0% RhB removal under an initial concentration of 10 mg/L within 30 min. This removal rate was approximately 65.8%, 57.7%, and 72.7% higher than that for a rGO/Bi2MoO6 (GBMO) binary composite, pure AgI powder, and pristine Bi2MoO6 nanoplates, respectively. The novel photocatalyst achieved approximately three times higher photocatalytic degradation within a shorter period of visible-light irradiation than pure Bi2MoO6. Through photoluminescence analysis and trapping experiments, this outstanding performance was attributed to the efficient separation of photogenerated electron-hole pairs owing to an internal electric field at the contact interface of AgI and Bi2MoO6, which generated more superoxide radical anions (•O2-) as primary reactive species to promote RhB degradation. Meanwhile, the rGO participated in the capture of visible-light and played a role of solid electronic medium at the AgI/Bi2MoO6 interface, which realized an effective Z-scheme electron transfer path, avoided the self oxidation of photocatalyst and prolonged the carrier life. Furthermore, the AGBMO-15 photocatalyst exhibited excellent photocatalytic degradation stability, maintaining an RhB removal rate of 96.2% after four cycles of reuse. Due to its simplicity, reusability, and controllability, the proposed photocatalyst has excellent application potential for the environmental remediation of wastewater.