From coal gangue to high-performance OER electrodes: Resource recovery and functional utilization of iron via...

Coal gangue is a bulk solid waste generated during coal mining, which requires urgent valorization due to its massive accumulation and high environmental risks. In this study, an electrodeposition-electrocatalysis coupling strategy was proposed to realize the resource recovery of iron ions from coal gangue leachates and their direct conversion into efficient oxygen evolution reaction (OER) electrodes. Inductively coupled plasma (ICP) analysis revealed that Fe was the most abundant element and exhibited the highest removal efficiency during electrodeposition (99 % at -6 V, k = 0.1098 h^-1), significantly surpassing Ti (93 %, k = 0.0849 h^-1) and Al (36 %, k = 0.0079 h^-1). The γ-FeOOH/NF electrode obtained by electrodeposition from Fe-enriched solution delivered remarkable OER activity in 1 M KOH, requiring overpotentials of only 284 mV and 303 mV at 50 and 100 mA cm^-2, respectively, with a Tafel slope of 162.7 mV·dec^-1, and maintained stable operation at 30.8 mA cm^-2 for more than 40,000 s. The performance approached the level of advanced non-precious-metal catalysts, while the waste-derived origin highlighted the originality and dual value of the strategy. This work provided a new paradigm that integrates environmental remediation with clean energy conversion.