Abstract

We report the photoelectrocatalysis of diclofenac sodium using a reactor consisting of Ag-BiVO4/BiOI anode and Ag-BiOI cathode. The electrodes were prepared through electrodeposition on FTO glass and modified with Ag nanoparticles through photodeposition. The structural and morphological studies were carried out using XRD, SEM, and EDS which confirmed the successful preparation of the materials. The optical properties as observed with UV-DRS revealed that the electrodes were visible light active and incorporation of metallic Ag particles on the surface increased the absorption in the visible light region. Presence of p-n heterojunction in the anode led to decrease in the spontaneous recombination of photoexcited electron–hole pairs as seen in the photocurrent response. The results from photoelectrocatalytic degradation experiments revealed that replacing platinum sheet with Ag-BiOI as counter electrode resulted in higher (92%) and faster removal of diclofenac sodium as evident in the values of apparent rate constants. The reaction mechanism further revealed that efficiently separated photogenerated holes played a major role in the degradation of the pharmaceutical. The prepared electrodes showed good stability and impressive reusability. The reports from this study revealed that the dual photoelectrodes system has a great potential in treating pharmaceutical polluted wastewater using visible light irradiation.

Highlights

  • We report the photoelectrocatalysis of diclofenac sodium using a reactor consisting of Ag-BiVO4/ BiOI anode and Ag-BiOI cathode

  • Much focus has been on the application of advanced oxidation techniques which are capable of complete mineralisation of organics for the removal pharmaceuticals in aqueous s­ olutions[6–8]

  • All the peaks of BiOI remained obvious in the XRD pattern of Ag-BiOI with no additional peak of metallic Ag and this could be due to low content of Ag in the material

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Summary

Introduction

We report the photoelectrocatalysis of diclofenac sodium using a reactor consisting of Ag-BiVO4/ BiOI anode and Ag-BiOI cathode. Unlike in typical photocatalysis, applied bias potential in PEC degradation significantly reduces the problem of spontaneous recombination of photogenerated electron–hole pairs because the potential provides sufficient force that creates electric field within the space-charge layer of the semiconductor which promote separation of charge carriers to the substrate and electrons can eventually be driven away from the photoanode or the semiconductor. Another interesting advantage of PEC is lower energy consumption when compared to anodic oxidation which requires high potential/current to facilitate degradation of o­ rganic[11]. In the works of Li et al, it was reported that the photodeposited Ag on ­BiVO4/MnOx formed a local magnetic field in synergy with heterojunction electric field through plasmonic resonance effect and this significantly improved charge separation resulting in better photocatalytic p­ erformance[33]

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