Tuning OH Adsorption via Pt Particle Size Control for Poisoning-Resistant Ammonia Oxidation

The practical utilization of ammonia electrolysis is limited by severe catalyst poisoning during the ammonia oxidation reaction (AOR) due to strong OH − adsorption on Pt anodes. Here, we demonstrate that controlling Pt particle size offers a scalable strategy to regulate OH − adsorption, thereby overcoming poisoning limitations. By systematically varying Pt size through simple thermal treatment, we modulated surface adsorption without introducing compositional or structural complexity. Specifically, larger Pt nanoparticles possess a higher fraction of terrace sites, which exhibit inherently weaker OH − binding than low-coordinated edge and corner sites, thereby mitigating catalyst poisoning. This tuning leads to a 1.4-fold enhancement in intrinsic AOR activity for the size-optimized Pt/C-800, achieved solely through particle size control without altering catalyst composition. Furthermore, the size-controlled catalyst shows superior poisoning resistance in a zero-gap electrolysis cell, achieving a current density 2.7 times higher than that of pristine Pt/C.