Innovative ternary bismuth oxychloride/bismuth oxide/carbon nanotubes induced excellent solar light-driven activity toward photomineralisation of diclofenac: Impact of metastable β-Bi2O3 inserted and electron-hole separation

Abstract

Solar energy-utilizing photocatalysts for water purification remain essential for environmental sustainability. This report presents new concepts in bismuth oxychloride/oxide/carbon nanotubes. (BiOCl/Bi2O3/CNT) composites, synthesized through a chemical deposition method involving BiOCl in a carbon nanotube bath, followed by surface reduction/oxidation steps. The impact of nanotube ratio and calcination temperature were explored. Characterization involved ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), elemental mapping, N2 adsorption/desorption analysis, and electrochemical impedance spectroscopy (EIS). XRD analysis revealed in-situ formation of α and β-Bi2O3 phases, rendering the composite more responsive to visible light at 200 °C. Carbon nanotubes reduced the band gap of ternary composites, yielding lower band gap energies in the visible range compared to BiOCl and Bi2O3. XPS analysis identified metallic Bi0 particles, enhancing electron mobility and charge separation. The synergy of BiOCl/Bi2O3/CNT-200 material significantly improved diclofenac degradation under solar simulator irradiation. Total organic carbon (TOC) analysis demonstrated 81 % mineralization with the BiOCl/Bi2O3/CNT-200 material. Active species trapping revealed the crucial roles of HO• radicals and h+ holes in pollutant degradation. The presence of the normally metastable β-Bi2O3 phase at 200 °C enhanced solar simulation efficiency, while carbon nanotubes acted as electron reservoirs, aided by Bi0 particles. The present study sets out an efficient composite synthesis approach for the photomineralization of complex pharmaceutical compounds.