Electrochemically Stabilized Iron Foam Enables Selective and Durable Nitrate-to-Ammonia Conversion at Industrial Current Densities

We report the synthesis and electrocatalytic performance of dynamic hydrogen bubble templated (DHBT) iron foams for the selective reduction of nitrate to ammonia, a novel strategy to mitigate nitrate pollution and add a decentralized route for ammonia production. The proposed catalyst Fe-foam_90s@Ti achieves up to 97% faradic efficiency (FENH3 ) and partial ammonia current density (jNH3 ) approaching -1 A.cm-2 under no external convection, outperforming all previously reported DHBT foams. Operando Raman spectroscopy and IL SEM studies reveal that the active state of metallic Fe is responsible for the high selectivity and increased current densities, while providing mechanistic insights into catalyst corrosion. Potential-dependent ICP-MS and ion chromatography studies identified the potential regimes of minimal Fe corrosion, which helped to demonstrate a suitable operating regime under extended electrolysis stress tests. In addition, the scalability of the catalyst was demonstrated by implementing it in an industrial model flow cell electrolyzer operating under galvanostatic conditions. The iron foams proposed in this study are highly effective catalysts for electrochemical nitrate reduction, offering a rare combination of low cost, scalability, and minimal environmental footprint. These results reinforce the potential of iron foam as an ideal electrocatalyst candidate for scaling up nitrate reduction, a compelling starter strategy for sustainable nitrogen management.