Highly-stable and efficient photocatalytic fuel cell based on an epitaxial TiO2/WO3/W nanothorn photoanode and enhanced radical reactions for simultaneous electricity production and wastewater treatment

Highlights: • The PFC is constructed with a novel epitaxial TiO₂/WO₃/W photoanode. • TiO₂/WO₃/W photoanode overcomes the drawbacks of both WO₃ and TiO₂ photoanodes. • The PFC is extremely stable and efficient for electric production and wastewater treatment. • Adding a small amount of Fe²⁺ significantly enhances the radical reactions. • The radical enhanced PFC shows improved energy output and organic degradation. Organic wastewater is a potential fuel because organic pollutants are rich in chemical energy. In view of the effluent treatment and simultaneous energy recovery, we proposed a highly efficient photocatalytic fuel cell (PFC) based on a novel, extremely stable and long-lived epitaxial WO₃ nanorod/TiO₂ nanothorn array (TiO₂/WO₃/W) photoanode. Owing to the epitaxial TiO₂ overlayer, which enhanced the separation and transfer of photogenerated carriers, and the inherent atomic-level protection for the photoanode from corrosion, the PFC showed improved performance in both energy output and wastewater treatment in comparison with a PFC based on a pristine WO₃ photoanode. Furthermore, a small amount of ferrous ions was added into the substrate solution to boost the charge transfer and the generation of hydroxyl radicals by introducing the radical reactions from the limited electrodes' surfaces into the whole aqueous system based on an electron-Fenton-like process. This radical-enhanced PFC (e-PFC) showed a high and stable conversion performance of organics into electricity: 0.761 V for open-circuit voltage, 3734 mA m⁻² for short-circuit current density, and 563 mW m⁻² for maximum power output; a removal ratio of 96% for degrading atrazine; and it maintained high-performance after 20 uses. It can be also successfully employed to generate electricity power and simultaneously degrade a large variety of refractory water pollutants. This work demonstrated the importance of interface design and system-level integration of high-performance nanomaterials on fabricating highly efficient PEC for possibly practical wastewater recycling.