Investigation of cubic Pt alloys for ammonia oxidation reaction

As a promising fuel candidate, ammonia has been successfully used as anode feed in alkaline fuel cells. However, current technology in catalysts for ammonia electro-oxidation reaction (AOR) with respect to both cost and performance is inadequate to ensure large scale commercial application of direct ammonia fuel cells. Recent studies found that alloying Pt with different transition metals and controlling the morphology of catalysts can improve the AOR activity, and thus potentially can solve the cost issue. Herein, (100)-terminated Pt-M nanocubes (M = 3d-transition metals Fe, Co, Ni, Zn) are synthesized via wet-chemistry method and their catalytic activities toward AOR are evaluated. The addition of Fe, Co, Ni and Zn elements can enhance the AOR activity due to decrease in oxophilicity of platinum and bifunctional mechanism. Pt-Zn exhibits the maximum mass activity and specific activity with values of 0.41 A/mg_Pt and 1.69 mA/cm² that are 1.6 and 1.8 times higher than Pt nanocubes, respectively. Pt-Fe, Pt-Co and Pt-Ni nanocubes also illustrate higher mass and specific activities compared to Pt nanocubes.