Desenvolvimento de fotoânodos de BiVO₄ por magnetron sputtering e sua aplicação na fotoeletro-oxidação de glicerol

Abstract

The increasing production of biodiesel generates significant amounts of glycerol as a byproduct. Improper disposal of this compound leads to environmental concerns and wastes a resource with economic potential. Sustainable strategies are therefore required to convert glycerol into higher-value products. Among the various conversion technologies, photoelectrocatalysis stands out by integrating solar energy with electrochemical reactions to enable selective transformations.Bismuth vanadate (BiVO₄) has emerged as a promising photoanode material due to its efficient visible light absorption and aqueous phase stability. In this study, BiVO₄ thin films were deposited via magnetron sputtering and evaluated for glycerol photoelectro-oxidation. Deposition parameters—including time, power, and gas flow rate—alongside thermal treatment conditions were systematically investigated.Morphological and structural characterizations by MEV, XRD, XPS, and UV-Vis spectroscopy confirmed the formation of monoclinic BiVO₄ with an optical bandgap of 2.8 eV. The optimized sample (50 min deposition, 50 W power, 50 sccm gas flow, with post-deposition annealing at 500 °C) exhibited a photocurrent density of 0.31 mA·cm⁻² at 1.23 V vs. RHE under simulated solar illumination. Photoelectrochemical tests performed in both stationary and flow cells (the latter fabricated by 3D printing) demonstrated enhanced current densities in the presence of glycerol and revealed that flow rate influenced product selectivity, notably producing glyceraldehyde, glycolic acid, formic acid, and lactic acid. These findings highlight the potential of magnetron sputtered BiVO₄ films for the photoelectrochemical valorization of glycerol and suggest further opportunities for performance improvement via cocatalyst incorporation, electrolyte optimization, and system integration.