High-Performance Electrochemical Nitrate Reduction to Ammonia under Ambient Conditions Using a FeOOH Nanorod Catalyst

Electrocatalytic nitrate reduction is promising as an environmentally friendly process to produce high value-added ammonia with simultaneous removal of nitrate, a widespread nitrogen pollutant, for water treatment; however, efficient electrocatalysts with high selectivity are required for ammonia formation. In this work, FeOOH nanorod with intrinsic oxygen vacancy supported on carbon paper (FeOOH/CP) is proposed as a high-performance electrocatalyst for converting nitrate to ammonia at room temperature. When operated in a 0.1 M phosphate-buffered saline (PBS) solution with 0.1 M NaNO₃, FeOOH/CP is able to obtain a large NH₃ yield of 2419 μg h^-1 cm^-2 and a surprisingly high Faradic efficiency of 92% with excellent stability. Density functional theory calculation demonstrates that the potential-determining step for nitrate reduction over FeOOH (200) is *NO₂H + H⁺ + e^- → *NO + H₂O.