Effect of electrode material on the electrochemical reduction of nitrogen in a molten LiCl–KCl–CsCl system

• Electrochemical reduction of nitrogen in molten chloride was investigated.
• Ti, Fe, Co, and Ni were attempted as cathode materials.
• The activity was the highest with Co, followed by Ni, Fe, and Ti.
• Electrical resistivity and wettability were determining factors for the performance.

A highly active electrode is a prerequisite to accelerate the sluggish nitrogen reduction in the otherwise promising molten alkali-metal chloride (LiCl–KCl–CsCl)-based ammonia synthesis process. In this study, four 3d metals, i.e., Ti, Fe, Co, and Ni, were selected and evaluated as candidate electrode materials. The electrochemical performance of each material was evaluated using linear sweep voltammetry (LSV) and chronoamperometry (CA). The activity in nitrogen reduction, described in terms of effective nitrogen reduction current, was in the order of Co > Ni > Fe > Ti. The variation in performance was ascribed to a synergetic relation between the electrical resistivity and wettability of the materials, indicating that both factors must be considered in selecting electrode materials, particularly in a molten-type system.