Catalytic roles and synergetic effects of iron-group elements on monometals and alloys for electrochemical oxidation of ammonia

Electrooxidation of NH₃ has gained extensive attention for energy and environmental applications such as fuel cells and water purification. In this study, carbon-supported simple metal-nanoparticle, binary- and ternary-nanoalloy (NA) catalysts composed of Fe-group elements, i.e., Fe, Co and Ni, were synthesized and their catalytic performance for NH₃ electrooxidation in alkaline media was investigated. Cyclic voltammetry and chronoamperometry revealed that Ni-containing catalysts show appropriate activities for NH₃ electrooxidation and the catalytic performances of Fe-group catalysts depend on affinity between constituent metals and nitrogen. Each Fe-group element exhibited distinctive catalytic features for the NH₃ electrooxidation, i.e., Ni ensured chemical stability, Fe effectively reduced overpotential and Co increased current density. The ternary NA catalyst showed excellent activities due to combination of all the catalytic features and synergetic effects exerted by the alloying.