A First Principles Study of Ammonia Electro-Oxidation for Fuel Cell Applications

Recently, there has been significant interest in finding alternative feeds to hydrogen for fuel cell applications. Direct methanol fuel cells (DMFCs), while addressing the transportation and storage issues of hydrogen suffers from CO poisoning and difficulties in on-board carbon capture. Ammonia presents a promising alternative feedstock because it is easily liquefied and its products (nitrogen and water) are environmentally benign. Here we present a first principles, density functional theory, analysis of electrochemical oxidation of ammonia. Using a simple electrochemical model [1, 2], the reaction is studied as a function of temperature, applied potential, and pH. Our study first focuses on the transition metals: Ta, Mo, W, Re, Os, Ru, Fe, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, and Au – allowing us to predict the onset potential and activity. From these results we determine optimal binding characteristics for a catalyst, which are used to screen for new materials. Promising candidates are studied to determine their ammonia electro-oxidation activity and onset potential.

References

1. Nørskov, J. K.; Rossmeisl, J.; Logadottir, A.; Lindqvist, L.; Kitchin, J. R.; Bligaard, T.; Jonsson, H., Origin of the overpotential for oxygen reduction at a fuel-cell cathode. Journal of Physical Chemistry B 2004, 108 (46), 17886-17892.

2. Nilekar, A. U.; Mavrikakis, M., Improved oxygen reduction reactivity of platinum monolayers on transition metal surfaces. Surface Science 2008, 602 (14), L89-L94.