A Dual Photoelectrode Photoassisted Fe-Air Battery: The Photo-Electrocatalysis Mechanism Accounting for the Improved Oxygen Evolution Reaction and Oxygen Reduction Reaction of Air Electrodes

Abstract

Effective utilization of solar energy in battery systems is a promising solution to achieve sustainable and green development. In this work, a photoassisted Fe-air battery (PFAB) with two photoelectrodes of ZnO-TiO₂ heterostructure and polyterthiophene (pTTh)-coated CuO (pTTh-CuO) grown on fluorine-doped tin oxide (FTO) is proposed. The band structure of semiconductors and the charge-transfer mechanism of heterostructure are studied. The electrochemical results show that the photogenerated electrons and holes play key roles in reducing the oxygen evolution reaction (OER)/oxygen reduction reaction (ORR) overpotential in the discharging and charging processes, respectively. The short-circuit current density, the open-circuit voltage, and the maximum power output of the PFAB can reach 34.28 mA cm^-2 , 1.15 V, and 5.69 mW cm^-2 upon illumination, respectively. The photoassisted Fe-air battery exhibits a low charge voltage of 0.64 V for ZnO-TiO₂ as photoelectrode and a discharge voltage of 1.38 V for pTTh-CuO as a photoelectrode at 0.1 mA cm^-2 .

Keywords: Fe-air batteries; heterostructures; photoassisted batteries; polymers.