Cooperative spin alignment enhances dimerization in the electrochemical ammonia oxidation reaction

Ammonia has recently attracted growing attention as a promising hydrogen carrier because it can be liquefied and stored in bulk under mild conditions. To fully harness its potential, more efforts are needed to elucidate and control the mechanisms of its decomposition. Here we show that intermediate dimerization processes proceed through a cooperative spin alignment effect between intermediates and can be promoted by the magnetic ordering rearrangement of magnetic substrates. We explored a series of Co/Pt magnetic thin-film catalysts as model materials to investigate spin-sensitive NH_x dimerization and eventual enhancement on catalytic activity. Through in situ spectroscopic analysis and theoretical verification, we demonstrate that coupling of N-NH with aligned net magnetic moments is the most favourable with the lowest energy barriers. This provides a precedent for understanding spin kinetics to help improve the catalytic efficiency of electrochemical ammonia decomposition.