Electrochemical Reduction Pathways from Goethite to Green Iron in Alkaline Solution with Silicate Additive

D Arumugam and TX Zhou and SN Jagadeesan and RT Pidathala and LH Zhang and AMM Abeykoon and G Kwon and D Olds and B Narayanan and XW Teng, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, 13, 2633-2640 (2025).

DOI: 10.1021/acssuschemeng.4c08451

Energy-efficient and low-temperature iron electrolysis in alkaline solutions is a low-cost and sustainable ironmaking process with zero- carbon emissions when renewable electrical sources are involved. However, its implementation is hindered by electrochemically inert Fe3O4 and parasitic H2 gas formation during the electrochemical reduction process, resulting in the low energy efficiency of iron electrolysis. Here, we further explore the potential of electrochemical reduction of goethite (FeOOH) by employing a low concentration of silicate additive in an alkaline solution to mitigate Fe3O4 accumulation and H2 generation. Electrochemical measurements coupled with operando X-ray diffraction and X-ray absorption spectroscopy suggested FeOOH -> Fe3O4 -> Fe(OH)2 -> Fe reduction pathways. Interestingly, a poorly crystalline or amorphous Fe(OH)2 phase formed in the NaOH/silicate mixed electrolyte, possibly due to the inhibitive effect of silicate on water and ion transport, which eventually contributed to the improved reduction of Fe3O4, also supported by atomistic simulations. This work demonstrates the potential for silicate as a low-cost and effective electrolyte additive to improve room-temperature green iron formation via electrolysis.

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