Electrocatalytic nitrate reduction to ammonia using a bifunctional Ni–Mo alloy catalyst

Abstract

The electrochemical nitrate reduction reaction (NO₃RR) using water as a hydrogen source provides opportunities for ammonia production but suffers from limited activity due to the difficulty of activating both H₂O and N-containing reactants under alkaline conditions. Herein, we report Ni–Mo alloys as efficient electrocatalysts for NO₃RR, among which Ni_2.44Mo exhibits an ammonia production activity of 1.3 A cm⁻² and a Faraday efficiency of 97% at a potential of −0.1 V vs. RHE, which are considerably higher than those of Ni, Mo and Ni–Mo alloys with other Ni : Mo atomic ratios. Experiments and DFT calculations showed that the Ni sites in the Ni–Mo alloy play major roles in promoting H₂O dissociation and forming hydrogen atoms for the conversion of N-containing intermediates. The Mo component promotes the conversion of NO₃⁻ to ammonia by enhancing NO₃⁻ adsorption and *NH hydrogenation processes. The bifunctional roles of Ni and Mo contribute to the high performance of Ni–Mo alloys. These findings highlight the rational design of NO₃RR electrocatalysts by simultaneously promoting the conversion of H₂O and N-containing species in alloy catalysts.