Portable photocatalytic fuel cell with anatase/rutile TiO₂ heterophase junction for solar energy harvesting and pollutant degradation

Abstract

Semiconductor photocatalytic electrodes are the core components for the efficient operation of photocatalytic fuel cell (PFC) systems, and enhancing their visible light response and photo-generated carrier separation are key strategies for improving PFC performance. In this study, a PFC consisted of an anatase TiO₂/rutile TiO₂ (ATO/RTO) photoanode and a silver cathode was designed. The experimental results indicate that the formation of a heterophase junction between ATO and RTO can expand the visible light absorption range and inhibited mitigates photogenerated carrier recombination. Therefore, with 1 mol/L NaOH as fuel, the ATO/RTO PFC achieves a photocurrent density of 0.6 mA/cm² and a maximum power density of 0.3 mW/cm² under simulated solar illumination, while the pure RTO and pure ATO PFCs exhibit photocurrent densities of 0.16 mA/cm² and 0.13 mA/cm², and power densities of 50 μW/cm² and 19.8 μW/cm², respectively. The photocurrent density of ATO/RTO PFC is higher than that of RTO PFC. Additionally, when utilizing 10 mg/mL methylene blue (MB) as fuel, the ATO/RTO PFC device achieved the remarkable photocurrent density of 0.43 mA/cm² and power density of 0.84 μW/cm². Simultaneously, ATO/RTO PFC demonstrated a peak degradation efficiency of 95.7% for MB. This PFC device enables both pollutant degradation and electricity generation, promising practical dual-function applications.