Avaliação fotocatalítica e fotoeletroquímica do NB2O5 decorado com prata e potencial degradação de corante reativo

Abstract

Water contamination due to the improper release of dye residues can result in irreparable effects on human life and the environment. Especially synthetic dyes with azo groups, due to their toxicity and carcinogenicity. Conventional methods are ineffective for removing this pollutant. Alternatively, POAs are promising and effective methodologies for removing these organic pollutants from wastewater. For example, photocatalytic degradation using semiconductors is considered an ecological and economical alternative for the mineralization of dyes. In addition, photoelectrocatalysis is also emerging as an alternative process that can be integrated into wastewater treatment, allowing for the simultaneous generation of an alternative source of energy, which is green hydrogen. Among semiconductors, niobium oxide stands out as the most widely available semiconductor in Brazil. Despite its many advantages, Nb2O5, the most thermodynamically stable state of the niobium-oxygen system, has a narrow light absorption range and is mainly activated by ultraviolet radiation. The aim of this work was to prepare heterostructured niobium oxide semiconductors with silver nanoparticles (Ag) for photocatalytic application in the degradation of the reactive blue dye 109 and photoelectrochemical studies for possible photoelectrocatalytic applications. Nb2O5was obtained using the Pechini methodology and the heterostructures were obtained by chemically reducing the mineral salt AgNO3 in different proportions, corresponding to the composites 21Nb2O5/Ag and 32Nb2O5/Ag. The synthesized materials were characterized using XRD, FTIR, DRS UV-Vis, SEM, HRTEM and XPS. The photocatalytic tests were carried out using a lamp that simulates the solar spectrum and the degradation efficiency was investigated using UV-Vis. The orthorhombic crystal structure of Nb2O5, as well as the formation of metallic Ag on its surface was confirmed, especially in 32Nb2O5/Ag. In addition, the morphology revealed particles of irregular size and shape, agglomerated and with an interconnected structure. After 120 minutes, 32Nb2O5/Ag showed significantly better photocatalytic performance than Nb2O5 with approximately 94% removal of the dye at a concentration of 5 mg L-¹, compared to only 9% obtained by Nb2O5. Following this result, the influence of dye concentration, the amount of catalyst and pH variation were also investigated. The photoelectrochemical responses were obtained by CV, LSV, chronoamperometry, EIS and Mott-Schottky curves, by depositing the materials on an ITO plate using thedip-coating method. The photocurrent results and the efficiency of the charge transfer carriers of the heterostructures were superior to Nb2O5. These results suggest that the Ag nanoparticle decorations carried out on Nb2O5 have extended its use, making it a promising material for photocatalytic and photoelectrocatalytic applications.