Anion Design Principles Governing Electrolyte Stability and Deposition Efficiency in Aqueous Iron Electrodeposition

Le résumé fourni par la source

Iron is essential to global manufacturing – from construction to transportation – yet its production remains capital-intensive and consumes nearly 7% of the world’s energy due to high-temperature processing requirements. Aqueous iron electrodeposition is attracting increasing interest as a route to room-temperature and potentially decentralized iron production for steelmaking. Essential to enabling this transformative technology is the discovery of new electrolytes that can enable efficient iron production at high rates using stable chemistries that are amenable to large-scale manufacturing. Anion-based coordination strategies have often been applied empirically to enhance iron electrodeposition efficiency; however, the molecular design principles that govern deposition efficiency and electrolyte stability remain underexplored. To identify these principles, we systematically explore a series of carboxylates with tunable structures by introducing functional groups with varying hydrophilicity and hydrogen-bond-donating ability. Our results reveal that only functional groups containing non-carboxylic protic hydrogen can form soluble Fe 2+ complexes at high concentration and elevated pH. We further observe that hydroxy-carboxylates exhibit greater solubility with Fe 2+ than amino-carboxylates at elevated pH, likely due to varying hydrophilicity. These findings highlight that both Fe–anion complexation and complex–solvent interactions critically determine electrolyte stability. Guided by these stability trends, we select citrate, malate, and tartrate – three carboxylates with varying coordination strengths, yet all capable of stabilizing Fe ions at higher pH – to probe how coordination structure correlates with electrodeposition efficiency and overpotential. Building on these insights, we design a new carboxylate anion that achieves a lower iron-reduction overpotential than these benchmarks while maintaining high iron deposition efficiency. This work establishes molecular-level guidelines for anion design and lays a foundation for developing next-generation, high-efficiency electrolytes for iron electrodeposition under mild pH conditions.

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