Cu-Doped Fe₂O₃ Nanorods for Enhanced Electrocatalytic Nitrogen Fixation to Ammonia

The electrochemical nitrogen reduction reaction (NRR) has emerged as a promising approach for synthesizing ammonia (NH 3 ) from nitrogen (N 2 ) under mild conditions. However, due to the difficulty in activating stable N 2 molecules and the competition with the hydrogen evolution reaction (HER), the development of active NRR electrocatalysts achieving a high NH 3 formation rate and a high Faradaic efficiency (FE) is strongly desired. Herein, Cu-doped hematite (Fe 2 O 3 ) nanorod arrays are synthesized by hydrothermal treatment and annealing under a N 2 atmosphere. At −0.15 V versus reversible hydrogen electrode (RHE), 4.4% Cu-doped Fe 2 O 3 exhibits a NH 3 formation rate of 12.5 μg h –1 mg cat. –1 and a FE of 16.4%, demonstrating a significant improvement in the NRR performance with Cu doping. The introduction of Cu increases the number of oxygen vacancies on the catalyst surface and induces charge redistribution between the constituent Cu and Fe ions, promoting the adsorption and activation of N 2 . Thus, this study not only offers an attractive earth-abundant NRR electrocatalyst but also provides an insight that heteroatom doping is effective to enhance the NRR activity through both defect engineering and electronic modulation.