Electrocatalytic Nitrate Reduction to Ammonia with a Bifunctional Ni-Mo Alloy Catalyst

Abstract

Electrochemical nitrate reduction reaction (NO₃RR) with water as hydrogen source provides opportunities for ammonia production but suffers from a limited activity due to the difficulty of activating both H₂O and N-containing reactants under alkaline condition. 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 −0.1 V vs. RHE, much higher than those of Ni, Mo and Ni-Mo alloys with other Ni: Mo atomic ratios. By experiments and DFT calculations, it is found that the Ni sites in the Ni-Mo alloy play major roles in promoting H₂O dissociation and the formation of hydrogen atoms for the conversion of N-containing intermediates. Mo component promotes the conversion of NO₃⁻ to ammonia via 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 promoting the conversion of H₂O and N-containing species simultaneously over alloy catalysts.