Uncovering interfacial electron transfer kinetics of WO3 biophotoelectrodes for food waste treatment

Abstract

An effective approach to enhance bioelectrochemical systems' performance involves leveraging semiconductors' light-harvesting capabilities alongside the catalytic properties of bacteria. Here, we demonstrate a food waste removal method using the integration of Shewanella oneidensis MR-1 with a tungsten(VI) oxide (WO₃) nanoplate photoanode in a solar-assisted microbial photoelectrochemical cell (S-MPEC) combined with silicon-based photovoltaics (SiPV). The S-MPEC integrates the technologies of bioelectrochemical cells with photoelectrochemical cells (PEC) to enhance the degradation of food waste. The bare WO₃ photoelectrode exhibits a photocurrent of 0.749 A m⁻² at 0.8 V under visible light, whereas the WO₃-MR-1 biophotoelectrode reveals a significantly higher photocurrent of 2.94 A m⁻². Under visible light exposure at an intensity of less than 100 mW cm⁻², the power densities of the WO₃ photoelectrode with and without MR-1 bacterial coating are 2.36 W m⁻² and 0.599 W m⁻², respectively. To further improve performance, the S-MPEC was connected with a SiPV. This combined system, PV-S-MPEC, achieved a power density of 21.99 W m⁻² and a chemical oxygen demand (COD) removal rate of 8167 mg L⁻¹ per day, demonstrating its effectiveness in degrading food waste hydrolysate. Additionally, the study of heterogeneous electron transfer kinetics indicated that the WO₃-MR-1 system exhibits more efficient diffusion coefficients and enhanced rate constants for reduction and oxidation reactions. These findings highlight the significant impact of photoexcited charge carriers on degradation performance in this complex hybrid electricigen system, underscoring its potential for developing S-MPECs for waste degradation. This study also demonstrates significant potential for reducing environmental impact through enhanced COD removal rates and energy-efficient waste processing, making it a viable solution for large-scale applications in urban waste management.