3DOM Fe/Co-containing perovskites as bifunctional ORR/OER electrocatalysts for a photo-rechargeable zinc battery

Three-dimensionally ordered mesoporous perovskites (La0.8Ba0.2Fe1–xCoxO3–δ (x = 0, 0.2, 0.4)), which are integrated with a silicon photovoltaic cell are prepared. Their overall solar energy conversion and storage efficiency in zinc-ion-based batteries was assessed. The electrocatalytic activities were measured in OER/ORR, while the galvanostatic charge/discharge processes were applied to study battery performance under 1 sun irradiation. The electronic properties of the electrocatalysts were determined by X-ray absorption and UV photoelectron spectroscopies. The importance of controlling the oxidation state of cobalt ions to increase the specific capacity and energy density of the batteries was shown. The ORR activity depends on oxygen vacancies, inferred from the XANES and EXAFS spectra analysis. Their presence is associated with the Co2+/Co3+ ratio which controls the beneficial eg orbitals occupancy via the high spin d7 electron configuration. Herein, we report an overall energy conversion efficiency of 12.6 % for the PV-integrated La0.8Ba0.2Fe0.8Co0.2O3–δ photo-rechargeable battery cell. [Display omitted] •The electrodes of La0.8Ba0.2Fe1–xCoxO3–δ are active in OER and ORR processes.•The electrodes were integrated with a PV cell to build a zinc-ion battery (ZIB).•The oxidation state of cobalt governs the performance of the photo-rechargeable ZIB.•The ORR activity depends on oxygen vacancies, as inferred from XANES and EXAFS.•The overall energy conversion efficiency of 12.6 % was achieved for the device.