Electrochemical Oxidation of Ammonia over Rare Earth Oxide Modified Platinum Catalysts

The recent development of anion exchange membranes (AEMs) has increased the potential and the importance of ammonia as a fuel for anion exchange membrane fuel cells (AEMFCs). Although electrocatalysts for ammonia oxidation using Pt-based alloy catalysts have been developed recently, no obvious activity enhancement was reported. In this paper, the electrocatalytic activity of rare earth oxide (RO: CeO2, Y2O3, La2O3, and Sm2O3) modified Pt catalysts for ammonia oxidation reaction was investigated in alkaline aqueous solutions. The ammonia oxidation activity was enhanced in accordance with the amount of OHad species on the electrode surface. From various electrochemical measurements, it was revealed that the RO additive improved the supply capacity of OHad to the reactive Pt sites. Among the catalysts studied, the CeO2-modified Pt electrocatalyst exhibited the highest activity; the peak current density for ammonia oxidation was 3.5 times higher than that of the Pt catalyst. Furthermore, this activity enhancement was also observed at 60 °C. These results indicate that the addition of RO is one of the promising ways to design the high performance anode for direct ammonia AEMFCs.