Towards continuous ammonia electro-oxidation reaction on Pt catalysts with weakened adsorption of atomic nitrogen

Abstract

One of the key challenges for ammonia-fed anion exchange membrane fuel cells is to the ammonia electro-oxidation reaction (AEOR) at anode, which has sluggish kinetics and generates atomic nitrogen (Nads) poisoning the Pt catalyst. In this study, a comparative study on Pt/Ta3N5, Pt/Ta2O5, Pt/carbon black, and Pt plate are conducted in order to clarify the promoting effect of the support materials for Pt catalysts. X-ray photoelectron spectroscopy analysis and density functional theory calculations reveal that the support materials significantly affect the electron condition of the Pt, resulting in the tuned adsorption energy of Nads on Pt surface. The electrochemical analysis demonstrates that the weakened adsorption of Nads lowers the coverage of Nads on Pt surface, resulting in the enhanced performance and stability of Pt catalysts for AEOR. In particular, Pt/Ta3N5 catalyst exhibits a current density of 5.92 mA cm−2 of AEOR at −0.34 V vs. SCE, which is higher than that of Pt/Ta2O5 (2.56 mA cm−2, −0.35 V vs. SCE) and Pt/C (4.45 mA cm−2, −0.26 V vs. SCE). The achievements in this study demonstrate the importance of controlling the type of supports for the development of an active electrocatalyst for continuous AEOR.