Optimizing Nitrate Reduction to Ammonia via Modulating Adsorption–Desorption Dynamics with High-Entropy CuNiCoZnMn Alloy Catalysts

Abstract

NO 3 RR synthesis of ammonia is a complex eight-electron reaction involving multiple steps and intermediates, in which NO 3 – adsorption and NH 3 desorption are crucial. The Cu-based high entropy quinary alloy catalyst has good surface adsorption and desorption ability for the reduction of nitric acid to ammonia. Here, the catalytic sites were coordinated by constructing CuNiCoZnMn alloys to adjust the electronic structure of the catalytic sites to facilitate the reaction of the substrate and thus optimize the whole reaction path. Based on the ternary alloy CuNiCo, the introduction of the Zn element continues to reduce the desorption energy barrier, and the introduction of the Mn element continues to enhance the initial adsorption energy so that the target product can be quickly held and released to accelerate the production of ammonia. The NH 3 yield and Faraday efficiency obtained for the quinary CuNiCoZnMn alloy catalyst reached 723.7 μmol h –1 cm –2 and 96.6%, respectively, at −0.35 V vs RHE potential. The density functional theory calculations showed that the quinary CuNiCoZnMn alloy (NO 3 – to *NO 3 – ) initial adsorption-free energy change and (*NH 3 to NH 3 ) NH 3 desorption-free energy change are −2.50, 0.072 eV, respectively, which are significantly better than those of the ternary CuNiC and quaternary CuNiCoZn of −2.02, 0.544 eV and −1.97, 0.217 eV.