The electrode modified with octahedral indium oxide catalyst with exposed high activity (222) crystal plane can suppress the hydrogen evolution side reaction and improve the reaction kinetics of chromium of iron-chromium flow batteries. The battery exhibits extremely high energy efficiency of 84.02% at an ultra-high current density of 140 mA·cm−2.
Abstract
Iron-chromium redox flow batteries (ICRFBs) show promise for large-scale energy storage, but their performance is hindered by the hydrogen evolution reaction (HER) and sluggish anode Cr3⁺/Cr2⁺ redox kinetics. Here, an octahedral In2O3 catalyst with exposed high-activity (222) crystal planes is reported, synthesized via high-temperature solution thermal decomposition and grown in situ on carbon cloth. The catalyst is grown in situ on carbon cloth to form a nanostructured indium-based electrode (In2O3-TCC). Grazing incidence wide-angle X-ray scattering confirms In2O3 phase formation, while XANES reveals abundant oxygen vacancies (Ov) serving as anode reaction active sites. In2O3-TCC exhibits enhanced electrochemical properties, including a tripled double-layer capacitance (8.92 mF cm−
2), a reduced charge transfer resistance (1.042 Ω), and improved Cr3⁺/Cr2⁺ kinetics. Density functional theory (DFT) shows that anode HER suppression arises from favorable H⁺ adsorption energy and a high desorption barrier. Furthermore, an in situ differential electrochemical mass spectrometer (DEMS) confirms effective anode HER suppression. The electrode achieves an energy efficiency of 84.02% at 140 mA cm−
2 and stable performance over 500 cycles. This work offers a new pathway for designing high-efficiency, long-lifetime ICRFB electrodes.
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