Optimization of the electron transfer kinetics between a photoanode and biocathode for enhanced carbon-neutral pollutant removal in photocatalytic fuel cells

Abstract

Photocatalytic fuel cells (PFCs) can harness energy from organic waste for electricity generation. However, incorporating CO₂ reduction into PFCs to achieve carbon neutrality remains a significant challenge due to substantial thermodynamic and kinetic barriers. Herein, a PFC is constructed using a formate dehydrogenase (FDH)-based biocathode and S-scheme heterojunction TiO₂/CdS engineered photoanode. The resulting PFC integrates photoanodic pollutant degradation with bio-cathodic CO₂ reduction to achieve a formate production rate of 7.13 μmol h⁻¹ with high selectivity and CO₂ recovery efficiency of 76.1%, which is the best value reported so far for PFCs. Furthermore, the PFC demonstrates a peak power density and current density of 186.3 μW cm⁻² and 1361.6 μA cm⁻², respectively. The best performance of the PFC is achieved due to the ultrafast electron transfer on the biocathode and the efficient carrier separation of the photoanode. The collaborative dynamics between the photoanode and biocathode lower the CO₂ reduction potential, enhancing the reaction kinetics of CO₂ reduction to formate.