Preparação e uso de eletrodos de frafite nanoestruturados de vanadato de bismuto na degradação fotoeletrocatalítica de radamina B isotiacianato

Abstract

Photoelectrocatalysis is a promising way to treat water contaminated by negative organic compounds. The use of BiVO4 nanoparticles supported on a conductive substrate allows the degradation of pollutants to be carried out under less energetic conditions. In this work, we report the degradation of Rhodamine B Isothiocyanto dye in a BiVO4/graphite (BVO@C) electrode performed under visible light irradiation through a photoelectrocatalytic process. The BiVO4 particles passed through ultrasonic irradiation by coprecipitation and then deposited on the surface of a graphite by the impregnation method. The 23 factorial design was used to optimize electrode fabrication. The electrode was characterized using SEM/EDS, XRD and DLS techniques. For the electrochemical characterization of the electrode, cyclic voltammetry (VC) and electronic impedance spectroscopy (EIS) were performed. The evaluation of the degradation of RhB isothionate was carried out in the processes of electrooxidation and photoelectrocatalysis, controlling or not controlling the temperature using the unmodified electrode and the BVO@C electrode. The characterization of the electrode confirmed the impregnation of the graphite with a BiVO4 particle through SEM/EDS, revealing specific peaks referring to vanadium (V), bismuth (Bi) and oxygen (O). The XRD analysis bought peaks related to the monoclinic phase of BiVO4, this fact being important due to the smaller band gap value, which implies activation of the semiconductor through light in the visible range. DLS and zeta potential analysis revealed negative charges on the surface of BVO@C, PDI values that indicated that the solution used for impregnation had monodispersive characteristics, which corroborated to a less regular impregnation, since this factor does not contribute to a deposition independent. Electrochemical analyzes confirm a considerable improvement of the modified electrode through a decrease in resistivity that may be associated with the presence of BiVO4, in addition to a decrease in hysteresis in relation to the emission/reduction pair. After 30 minutes, the degradation results in the electrocatalysis (EC) and photoelectrocatalysis (PEC) system, the results were considered relevant, reaching almost 100% of the dye being degraded, with a higher degradation rate for the photoelectrocatalysis experiments in relation to electroxidation, and higher values in experiments in which temperature was not controlled. To analyze the electrode reuse cycles, several reuse cycles were performed and the electrode efficiency (BVO@C) was observed. After nine cycles of reuse of the BVO@C electrode, it was observed that it presented more than 80% of RhB efficiency. and photoelectrocatalysis of dyes from industrial effluents.