Electrocatalytic reduction of nitrate into ammonia by bimetallic copper‑nickel catalysts

Electrochemically converting nitrate (NO 3 − ) to ammonia (NH 3 ) powered by renewable energy sources offers a sustainable alternative pathway for NH 3 synthesis. Herein, bimetallic Cu Ni nanoparticles supported by carbon paper (CP) were synthesized using a facile electrodeposition method. The structures of the resulting samples were characterized by scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The activity of the samples toward nitrate reduction reaction (NO 3 RR) was evaluated by linear sweep voltammetry, electrochemical impedance spectroscopy and chronoamperometry tests. The products from NO 3 RR were also determined. Compared to the counterpart catalysts including Cu/CP and Ni/CP, the CuNi/CP catalyst with bimetallic phases showed much higher faraday efficiency (FE) and yield for the NO 3 RR. The NO 3 RR catalyzed by CuNi/CP catalyst suggested a tandem mechanism in which Cu is responsible for the reduction of NO 3 − into NO 2 − , while Ni is favorable for the generation of H atoms (H*), which subsequently promotes the further conversion of NO 2 − and other intermediates to NH 3 .Benefiting from the synergistic effects of Cu and Ni, the optimal CuNi/CP catalyst efficiently converted NO 3 − to NH 3 with a high FE of 90.36 % and NH 3 yield of 3.53 mg h −1  mg −1 at −0.6 V vs. RHE in 0.5 M Na 2 SO 4  + 0.1 M NaNO 3 solutions.