Avaliação do efeito piezoelétrico no desempenho fotocatalítico de amostras de niobato de bismuto

Abstract

Due to the wide range of environmental impacts caused by the rampant use of fossil fuels, the search for clean energy sources has become increasingly relevant. In particular, the use of solar energy through the photocatalysis technique has gained prominence, as it enables the degradation of pollutant compounds and the production of clean fuels. Piezophotocatalysis surges as an emerging field in this context, enabling the increase in photocatalytic efficiency through the use of piezoelectric materials, capable of generating an electric field from mechanical disturbances in their structure, contributing to a greater stabilization of the e-/h+ pairs. Thus, the present work aims to evaluate the effect of piezoelectric activation on the photocatalytic performance of bismuth niobate (BiNbO4) samples synthesized by the hydrothermal method. The materials were prepared at different pH values, starting from stoichiometric amounts of Bi(NO3)3.5H2O and niobium ammonium oxalate that were subjected to hydrothermal treatment at 200 °C and 24 hours and subsequent calcination at 500 and 700 °C. At pH 8 and calcination at 500ºC, the preferential formation of the a-BiNbO4 phase is observed, while at 700ºC, a mixture of phases between a- BiNbO4 and Bi5Nb3O15 is obtained. Piezophotocatalytic tests revealed a higher piezoelectric activation for the pH 8 700 °C sample, which obtained a 96% increase in the degradation rate of methylene blue, compared to regular photocatalysis, as well as an increase of approximately eight times in the oxidation rate of methanol. EPR analyses revealed that the primary photocatalytic mechanism is the major activation pathway in the sample. In addition, this sample also exhibited a 422% increase in the degradation rate of the emerging contaminant fipronil, and an H2 production of 130.64 umol.g-1.h-1, via the piezophotocatalytic pathway, evidencing its potential for both environmental and energetic applications.