Dual photoelectrode-drived Fe–Br rechargeable flow battery for solar energy conversion and storage: A cost-effective approach

The integrated design of solar energy conversion and storage systems has attracted increasing attention, and non-spontaneous redox reactions driven by dual photoelectrodes provide a potential solution to this issue. This study presents a solar rechargeable flow battery (SRFB) that combines dual photoelectrodes (BiVO 4 or Mo–BiVO 4 as photoanode, polyterthiophene (pTTh) as photocathode) with cost-effective redox pairs (Fe 3+ /Fe 2+ and Br 3 − /Br − ). The system charges under simulated solar illumination (100 mW∙cm −2 , AM 1.5G) and releases stored energy controllably as electrical energy. Research indicates the Mo–BiVO 4 photoanode and pTTh photocathode achieve an open-circuit voltage of 0.34 V and a short-circuit current density of 0.38 mA cm −2 . Using a specially designed Fe 3+ /Fe 2+ -Br 3 − /Br − (Fe–Br) SRFB device made via 3D printing, a charging photocurrent of approximately 1.9 mA cm −2 is attained. In constant current discharge tests, an initial discharge voltage of 0.23 V is observed at 0.1 mA∙cm −2 within the 10 discharge cycles, demonstrating system stability and offering a viable solution for low-cost, large-scale solar energy storage and conversion.