The electrochemical ammonia oxidation reaction (AOR, NH₃ → N₂) can be used in ammonia fuel cells, ammonia decomposition for hydrogen production, and ammonia energy conversion processes. For Pt-based catalysts, AOR typically involves partial dehydrogenation of NH₃ to form NHx intermediates such as *NH₂, *NH, and *N. These intermediates then undergo NHx–NHy coupling to form N–N bonds, and finally, further dehydrogenation to generate N₂. In this Nature Chemistry article, the authors argue that the most challenging step in AOR is the dimerization and bonding process between the NHx intermediates, a process that can be influenced by the spin state of the catalyst surface.