CONVERSÃO FOTOELETROQUÍMICA DE METANO EM ENERGIA UTILIZANDO FOTOCÉLULAS A COMBUSTÍVEL BASEADAS EM FOTOÂNODOS DE BiVO4/CoOx

Abstract

Climate change associated with greenhouse gas emissions has driven the search for technologies capable of mitigating environmental impacts while simultaneously enabling sustainable energy generation. In this context, methane stands out due to its high global warming potential and elevated energy content, making it a strategic target for energy valorization processes. Among the available conversion technologies, photoelectrocatalysis emerges as a promising approach by employing solar energy to drive electrochemical reactions, combining energy recovery with environmental mitigation. This work investigates the performance of a methane-fed photo fuel cell (PFC) based on bismuth vanadate (BiVO4) photoanodes surface-modified with cobalt oxide (CoOx). BiVO4 has attracted significant attention as a photoanode material due to its suitable band gap of approximately 2.4 eV, enabling visible light absorption, chemical stability in aqueous solution, and relatively low cost, making it attractive for photoelectrochemical applications. The photoanodes were synthesized by electrodeposition followed by thermal conversion, while the CoOx cocatalyst was deposited on the surface through chemical impregnation and thermal treatment. Structural, morphological, optical, and electronic characterizations confirmed the preservation of the monoclinic phase of BiVO4, with an unchanged band gap of 2.46 eV, indicating that the modification predominantly affects the semiconductor/electrolyte interface. Mott–Schottky analysis revealed a shift in the flat-band potential from −0.02 to 0.15 VRHE and an increase in charge carrier density after CoOx modification. Electrochemical impedance spectroscopy demonstrated a significant reduction in polarization resistance, indicating improved charge transfer kinetics. During PFC operation, the BiVO4/CoOx photoanode exhibited a 64% increase in maximum power density when the anolyte was saturated with methane, reaching 0.38 mW under continuous flow conditions. These results demonstrate that the use of CoOx as a cocatalyst is an effective strategy to enhance the photoelectrochemical performance of BiVO4, highlighting the potential of this system for methane energy valorization and sustainable electricity generation.