Pulse-Plating Electrodeposition of Metallic Bi in an Organic-Free Aqueous Electrolyte and Its Conversion into BiVO₄ To Improve Photoelectrochemical Activity toward Pollutant Degradation under Visible Light

Abstract

A low-cost and durable BiVO 4 photoelectrode (PE) is herein synthesized to improve the separation of the electron and hole pair in photoelectrochemical applications. A new synthesis method was envisaged depositing metallic Bi on fluorine-doped tin oxide (FTO) in a pure aqueous electrolyte containing Bi(NO 3 ) 3 and KI via pulse plating at room temperature (pH = 1). The Bi 0 and intermediate oxides/hydroxides in low content were then transformed into BiVO 4 using thermal treatments. This procedure renders a rapid and low-cost fabrication method, enhancing the catalyst durability. Xray diffraction and X-ray photoelectron spectroscopy analysis confirmed the composition of the Bi intermediate species during synthesis and the successful deposition of a monoclinic phase of BiVO 4 . An optical band gap of 2.42 eV with n-type semiconductive features was estimated for the BiVO 4 . An energy band diagram was proposed based on diffuse reflectance spectroscopy analysis and Mott−Schottky plots showing that the BiVO 4 surface was thermodynamically unfavorable to produce hydroxyl radicals. However, this PE presented a relevant photoelectrochemical activity under low energy illumination (Xe lamp) to conduct the degradation of pollutants via direct oxidation. Under this condition, the highest degradation percentage of sulfamethoxazole was achieved in photoelectrocatalysis (around 50%) in comparison with electrocatalysis, photolysis, and photocatalysis techniques. The FTO-BiVO 4 catalyst displayed adequate photostability and reusability during all testing.

Unlocking a Type-II CoO@BiVO4 Heterostructure for Wastewater Purification

“…To determine the type of semiconductor, appraise the flat band potential ( E fb ), and estimate the carrier density ( N D ), the Mott–Schottky diagrams were tested (Figure a). The slopes of Mott–Schottky for Ti/BiVO 4 , Ti/CoO, and the Ti/CoO@BiVO 4 electrodes were positive, indicating that they were all n-type semiconductors, consistent with the previous literature . For N D , its value is proportional to the inverse of the slope of the Mott–Schottky plot based on the eq (S1) in the Supporting Information.…”

“…The slopes of Mott−Schottky for Ti/ BiVO 4 , Ti/CoO, and the Ti/CoO@BiVO 4 electrodes were positive, indicating that they were all n-type semiconductors, consistent with the previous literature. 40 For N D , its value is proportional to the inverse of the slope of the Mott−Schottky plot based on the eq (S1) in the Supporting Information. Further, a more negative E fb indicates more considerable band bending, accelerating charge separation at the semiconductor/ electrolyte interface.…”

“…There was no apparent difference in dark current intensity between the single-component and heterostructure electrodes. The photocurrent intensity of the Ti/CoO@BiVO 4 -2 M electrode was much higher than that of Ti/CoO and Ti/BiVO 4 , which is conducive to generating higher carrier density in the PEC process …”

3D Biomimetic Hydrangea-Like BiOCl and PtNi Nanocube-Based Electrochemical Immunosensor for Quantitative Detection of CA19–9

“…Recently, bismuth-based materials have been developed at an explosive speed on account of their wide distribution and excellent physicochemical properties. They have been extensively applied toward the degradation of organic dyes 17,18 and the detection of environmental pollutants, 19 as well as being used as a carrier for chemoradiation therapy. 20 Among the many bismuth-based materials reported to date, bismuth oxychloride (BiOCl) is one of the most important semiconductor materials derived from the V-VI-VII group, which exhibit a tetragonal crystal system.…”