Síntese e otimização de fotocátodos de Cu2O/CuO e fotoânodos de BiVO4/CoOx aplicados em células a combustível fotocatalíticas alimentadas por glifosato e CO2.

Abstract

As climate change intensifies and concerns about the environmental impacts of fossil fuel-based energy sources grow, the search for more sustainable and cleaner alternatives has become a global priority. Photocatalytic fuel cells (PFCs), which convert solar energy into chemical (and consequently electrical) energy, offer a promising solution in this context. This work presents the development and optimization of photocatalytic fuel cells based on BiVO₄/CoOx (photoanode) and Cu₂O/CuO (photocathode) photoelectrodes, focusing on CO₂ reduction and glyphosate oxidation. Half-cell results showed significant photocurrent gains after thermal treatment of Cu₂O films, which promoted the formation of a Cu₂O/CuO heterostructure, facilitating charge separation and increasing carrier density. The modification of BiVO₄ with a CoOx cocatalyst resulted in a shift of the Onset potential to more negative values and a significant increase in photocurrent, indicating more efficient hole extraction and reduced surface recombination. Electrochemical impedance spectroscopy (EIS) analyses revealed a decrease in charge transfer resistance in both Cu₂O/CuO and BiVO₄/CoOx films, associated with an increase in the number of carriers available for redox reactions. In tests under different atmospheres, the presence of CO₂ in the cathodic compartment considerably increased the photocurrent density, while glyphosate acted as a fuel, further improving the system’s efficiency. The full cell, operating in borate electrolyte with glyphosate and saturated with CO₂, reached an open-circuit voltage of 0.63 V, a photocurrent density of 0.58 mA/cm², and a maximum power density of 0.05 mW/cm². These results demonstrate that photoelectrode engineering, through thermal treatments and cocatalyst addition, is essential to maximize charge separation, reduce resistive losses, and optimize both energy conversion and pollutant degradation in photoelectrochemical systems.