Electrochemical-mediated FeS active sites regeneration for effective extraction of uranium from seawater

Electrochemical uranium extraction (EUE) from seawater offers a sustainable pathway for nuclear fuel production, yet its practical implementation remains hindered by active site deactivation, limited selectivity, and high operational costs. To overcome these challenges, we developed a nano-FeS-modified carbon cloth (nFeS/CC) electrode via an anaerobic in situ deposition strategy, enabling the construction of an advanced EUE system with efficient and selective UO₂²⁺ adsorption-reduction performance and regenerable active sites. Experimental results and density functional theory calculations revealed that interfacial sulfur species strongly coordinate with UO₂²⁺ through Lewis complexation. The adsorbed UO₂²⁺ was effectively reduced to low-valent, insoluble uranium oxides (U_xO_y) via both Fe(II)-mediated surface redox reactions and direct electroreduction. Remarkably, the FeS active sites exhibited in situ electro-regenerability, ensuring sustained catalytic activity over multiple operations. Additionally, the generation of reactive oxygen species under electrochemical conditions enhanced uranium extraction by improving UO₂²⁺ bioavailability, lowering the activation energy barrier, and promoting interfacial electron transfer. The EUE system exhibited excellent selectivity over competing metal ions and demonstrated robust stability. Evaluations in NaCl solution, simulated seawater, and real seawater confirmed the nFeS/CC system's high adaptability, operational stability, and economic feasibility, achieving uranium extraction capacities up to 17154 mg g⁻¹ and a low energy cost of approximately 2.1 USD kg⁻¹ U. This work offers new insights into the design of durable and cost-effective electrochemical platforms for uranium recovery from complex marine environments.