Recycling iron and steel is critical for environmental sustainability and essential to close material loops in circular economics. A major challenge is to produce high-value products and to control impurities like carbon in the face of stringent consumer requirements and volatile markets. Here, we develop an electrorefining process that directly decarburizes molten iron by imposing an electromotive force between it and a slag electrolyte. Upon anodic polarization, oxide anions from the slag discharge directly on carbon dissolved in molten iron, evolving gaseous carbon monoxide. In a striking departure from conventional practice that highly relies on reaction with solubilized oxygen, here electrorefining achieves decarburization by direct interfacial reaction. We demonstrate that this technique produces ultra-low-carbon steels and recovers silicon as a by-product at the cathode, requiring a low energy input and no reagents. We expect this process to be scalable and integrable with secondary steel mills.

回收钢铁对于环境可持续性至关重要，对于关闭循环经济中的材料循环至关重要。面临严格的消费者要求和动荡的市场，一个主要的挑战是生产高价值产品并控制碳等杂质。在这里，我们开发了一种电解精炼工艺，通过在铁水和炉渣电解质之间施加电动势来直接使铁水脱碳。在阳极极化时，炉渣中的氧化物阴离子直接放电到溶解在铁水中的碳上，放出气态一氧化碳。与高度依赖与溶解氧反应的传统做法截然不同，这里的电解精炼通过直接界面反应实现脱碳。我们证明该技术可生产超低碳钢并在阴极将硅作为副产品回收，需要低能量输入且无需试剂。我们希望这个过程可以扩展并与二级钢厂集成。