Effect of Mo on Ammonia Oxidation Activity of Pt Electrocatalyst

Abstract

In recently years, hydrogen production by water electrolysis using renewable energy is promoted from a carbon-neutral perspective. However, hydrogen is difficult to store and transport, and low volumetric energy density. Therefore, ammonia obtained by the Haber-Bosch process is attracting much attention as an energy carrier because of its easy liquefaction and handling. Ammonia is toxic, but it can be detected easily if ammonia leaks outside owing to its characteristic smell. Thus, a direct ammonia fuel cells (DAFCs) that use ammonia as fuel is promising candidate as a new power generation system. Generally, Pt is used as anode catalyst for ammonia oxidation reaction in DAFC. But it is desired to develop an alternative catalyst for DAFC anode due to the price escalation of Pt, limitation of Pt reserves and the problems of inactivation caused by N_ads poisoning on Pt. Therefore, Pt-Mo alloy catalyst was prepared by RF-magnetron sputtering and the ammonia oxidation activity was investigated in this study. Pt-Mo alloy catalysts showed higher ammonia oxidation activity than Pt one. Especially, Pt-44.0at％Mo indicated 31.4 mA cm⁻² and it is the highest activity among Pt-Mo alloys. And then, Pt-44.0at％Mo is promising candidate for anode catalyst of DAFC.

Fig. 5　Ammonia oxidation activity of Pt, Pt-19.7at％Mo, Pt-44.0at％Mo and Pt-90.8at％Mo thin films.