Desenvolvimento de sistemas eletroquímicos explorando materiais à base de BiNbO4 e BiVO4

Abstract

This work describes the development of a novel photoelectrochemical platform using bismuth vanadate (BiVO4) and bismuth niobate (BiNbO4)-based materials for the detection of gallic acid (GA), as well as for the development of an electrochemical supercapacitor. In this sense, samples based on BiNbO4 (BNO), prepared via molten salts synthesis, were combined with samples based on BiVO4 (BVO) and compared with each other in order to identify the most photoelectroactive material for GA detection. The materials were analyzed by X-ray diffraction (XRD), electrochemical impedance, voltammetry, amperometry, as well as charge and discharge tests. XRD analysis demonstrated that the molten salt-based method for obtaining the materials was capable of generating the orthorhombic structure of BiNbO4 (α-BiNbO4) and the triclinic structure of BiNbO4 (β-BiNbO4), as well as an impurity related to the formation of BiOCl. The amperometric responses of the materials revealed that the material based on bismuth vanadate and bismuth niobate (BVO/BNO) presented a greater photoelectrochemical response to GA. Electrochemical impedance measurements indicated that the carrier density in BVO/BNO/FTO was approximately 30% higher than that observed for BVO/FTO and approximately 50% higher than that observed for BNO/FTO. After identifying the most efficient platform, a glass slide coated with fluorine-doped tin oxide was modified with the composite and used for the detection of the gallic acid molecule. Under optimized conditions, the BVO/BNO/FTO platform exhibited a linear response range between 1 and 165 μmol L-1. Additionally, cyclic

voltammetry electrochemical tests revealed a high specific capacitance value (474,45 Fg- 1

), highlighting the potential of BVO/BNO for applications in the development of electrochemical supercapacitors.