Evaluating the size of Fe nanoparticles for ammonia adsorption and dehydrogenation

Abstract The interaction of NH 3 with different Fe clusters and nanoparticles was evaluated using a periodic density functional theory method. The preferred adsorption sites, adsorption energies of NH 3 , the transition states and the corresponding activation energies of the first NH 3 dehydrogenation reaction on different small Fe nanoparticles were compared with those obtained for bare Fe(1 1 1) and Fe(1 1 1) with an adatom. On seven clusters investigated (Fe 16 , Fe 22 , Fe 32 , Fe 59 , Fe 80 , Fe 113 and Fe 190 ), NH 3 was found to adsorb on top sites, while the NH 2 and H products adsorb on bridge and hollow sites, respectively. Higher NH 3 adsorption energies were obtained and the dehydrogenation reaction was found to be more exothermic when the size of clusters increases. Although similar activation barriers were found for different nanoparticles and bare surfaces, the NH 3 first dehydrogenation is favored when the size of nanoclusters increases.