Surface Obstacles in Ammonia Oxidation on Platinum: What Drives Catalyst Deactivation?
Geraldo Novaes Tessaro, Rodrigo Gomes de Araujo, Joelma PerezABSTRACT
Deciphering the surface processes that drive catalyst deactivation during ammonia oxidation reaction (AOR) on platinum is a longstanding challenge in electrocatalysis. Here, by combining online electrochemical mass spectrometry (OLEMS) with high‐area Pt/C surfaces, we have established numerous electrochemical protocols to probe surface‐blocking species as a function of potential. Pt surface oxide formation emerges as the decisive driver of catalyst deactivation, dictating the AOR pathways and electrocatalytic activity, while simultaneously promoting the formation of poisoning species. Unprecedentedly, poisoning species formed in the Pt oxide region (N, NH, N 2 O, and NO) were recognized by their stripping signatures, that is, N 2 , NO, and N 2 O, with N 2 predominating. Furthermore, a set of control experiments unequivocally demonstrated that the detected species originate exclusively from poisoning intermediates, as evidenced by measurements in the absence of NH 4 OH, pre‐ and post‐AOR x‐ray photoelectron spectroscopy (XPS) analysis of the electrode, isotopically labeled ammonium ( 15 NH 4 OH), and reduction of soluble AOR products. These findings directly impact the design of electrochemical energy conversion systems involving ammonia.