Sacrificial Dopant to Enhance the Activity and Durability of Electrochemical N2 Reduction Catalysis

Abstract

Electrochemical nitrogen reduction reaction (eNRR) is a promising alternative to the Haber-Bosch process for environmentally sustainable ammonia synthesis. However, the reduction of the dinitrogen molecule to ammonia is known for its extremely sluggish kinetics, and the catalytic activity and selectivity of eNRR catalysts remain significantly low for practical deployment of the technology. Herein, a sacrificial dopant for eNRR catalysts is introduced in order to improve the activity and durability of the electrochemical N-2 reduction catalysis. Specifically, iridium-doped mesoporous copper sulfide hexagonal prism nanoparticles provide an ammonia production yield of 18.2 +/- 0.8 mu g/h cm(2) at -0.6 V-RHE and a Faradaic efficiency of 2.4 +/- 0.1% in neutral aqueous electrolytes. The dopant modifies the electronic states of the eNRR active site to achieve appropriate *N2H and *H adsorption energies. The doping process also results in an increased active surface area of catalyst particles along with a 3-fold increase in durability compared to the undoped copper sulfide, thus further enhancing the eNRR activity. Last, the developed eNRR catalyst is employed in a practical ammonia production device displaying a production yield of 1.1 mu g(NH3)/h cm(2) at 1.8 V-cell. The present results suggest a design factor to enhance the catalyst durability, that is, by the introduction of a sacrificial dopant, in the development of efficient eNRR catalysts for electrochemical ammonia production.