Arumugam Divakar, Zhou Tongxin, Jagadeesan Sathya Narayanan, Pidathala Ranga Teja, Zhang Lihua, Abeykoon Am Milinda, Kwon Gihan, Olds Daniel, Narayanan Badri, Teng Xiaowei
Department of Chemical Engineering, Worcester Polytechnic Institute, 100 Institute Road, Worcester, Massachusetts 01609, United States.
Department of Mechanical Engineering, University of Louisville, 332 Eastern Pkwy, Louisville, Kentucky 40292, United States.
ACS Sustain Chem Eng. 2025 Feb 11;13(7):2633-2640. doi: 10.1021/acssuschemeng.4c08451. eCollection 2025 Feb 24.
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 FeO and parasitic H 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 FeO accumulation and H generation. Electrochemical measurements coupled with operando X-ray diffraction and X-ray absorption spectroscopy suggested FeOOH → FeO → Fe-(OH) → Fe reduction pathways. Interestingly, a poorly crystalline or amorphous Fe-(OH) 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 FeO, 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.
在碱性溶液中进行的节能低温铁电解是一种低成本且可持续的炼铁工艺，当使用可再生电源时可实现零碳排放。然而，在电化学还原过程中，电化学惰性的FeO和寄生性H气体的形成阻碍了该工艺的实施，导致铁电解的能量效率较低。在此，我们通过在碱性溶液中使用低浓度的硅酸盐添加剂来减轻FeO的积累和H的生成，进一步探索了针铁矿（FeOOH）电化学还原的潜力。电化学测量结合原位X射线衍射和X射线吸收光谱表明了FeOOH→FeO→Fe-(OH)→Fe的还原途径。有趣的是，在NaOH/硅酸盐混合电解质中形成了结晶性差或无定形的Fe-(OH)相，这可能是由于硅酸盐对水和离子传输的抑制作用，最终有助于改善FeO的还原，这也得到了原子模拟的支持。这项工作证明了硅酸盐作为一种低成本且有效的电解质添加剂，通过电解改善室温下绿色铁形成的潜力。
