Construction of M-BiVO4/T-BiVO4 isotype heterojunction for enhanced photocatalytic degradation of Norfloxacine and Oxygen evolution reaction

Abstract

To conquer the issues of poor compatibility, confined intimate contact and limited improvement of charge anti-recombination process of a traditional heterojunction formed by interfacing of two different semiconductors, a simplistic strategy has been espoused for the fabrication of isotype heterojunction flanked with two dissimilar crystal phases of a single semiconducting material. Herein, we account the fabrication of an in-situ formed M-BiVO₄/T-BiVO₄ (MT-BiVO₄) isotype heterojunction by a simple co-precipitation method followed by altering the calcinations temperatures. The physico-chemical properties of the fabricated MT-BiVO₄ isotype hetrojunctions were analyzed by using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-Visible Diffuse reflectance spectroscopy (UV-Vis DRS) techniques. The FESEM image of MT-BiVO₄ photodeposited by Au and MnOx particles was provided strong evidence for the spatial separation of photogenerated charge carriers between M and T phase of BiVO₄ in an isotype heterojunction. The interfacing of T-BiVO₄ with M-BiVO₄ in an isotype heterojunction affords the well-built close contact between them was confirmed by the High resolution transmission electron microscopy (HRTEM) analysis. The photocatalytic reactions of all the prepared MT-BiVO₄ isotype heterojunctions were examined by monitoring the degradation of Norfloxacine and oxygen evolution reaction under visible light irradiation. The optimized 65% MT-BiVO₄ isotype heterojunction discloses higher photocatalytic activity around 91% of Norfloxacine degradation in 150 min and 808 µmol of O₂ evolution in 2 h under visible light irradiation. On the other hand, the photoelectrochemical measurements reveals that the optimized 65% MT-BiVO₄ isotype heterojunction exhibits superior photocurrent i.e. 584 µA/cm² which is approximately 5.1 and 25.3 times higher than the neat T-BiVO₄ and M-BiVO₄, and these results are well consistent with the photocatalytic activities. The higher PEC and photocatalytic activities are due to the well-built close contact, superior compatibility and matching band structure between T-BiVO₄ and M-BiVO₄, which provides strapping driving force for the efficient enhancement of charge separation process. The Electrochemical impedance spectroscopy (EIS), photoluminescence (PL), photoelectrochemical (PEC) and bode analysis confirms the effectual diminish of charge recombination process in MT-BiVO₄ isotype heterojunction relative to the neat materials. The chronoamperometric analysis authenticated that the isotype heterojunctions are more stable than the neat materials.

Keywords: Isotype heterojunction; MT-BiVO(4); Norfloxacine degradation; O(2) evolution; Spatial separation.