Fe-doped CuO embedded in carbon nanosheets for efficient and selective nitrate electroreduction to ammonia

The nitrate electroreduction reaction (NO3-RR) provides a low-carbon and environmentally friendly strategy for ammonia production. Here, a sustainable method for synthesizing carbon nanosheets is developed by assembling biomass molecules on a boric acid template, followed by thermal annealing. During this process, the introduction of Fe3+ and Cu2+ ions enables the formation of Fe-doped CuO nanoparticles embedded in carbon nanosheets (Fe-CuO/C). The Fe-CuO/C shows high activity for the NO3-RR resulting in a low potential of 0.089 and -0.192 V vs. RHE at -10 and -50 mA cm-2, with high ammonia yield and faraday efficiency. Theoretical calculations indicate that the *NO to *NOH step is the rate-determining step during the NO3-RR. The doping of Fe effectively reduces the energy barrier of this step.