Hydrogen from formic acid decomposition over Pd and Au catalysts

Vapour phase decomposition of formic acid has been studied systematically over a range of catalysts: 1.0 and 10 wt.% Pd/C, 0.8 wt.% Au/C and 1.0 wt.% Au/TiO₂. The mean metal particle size of these materials was estimated by HRTEM and turnover frequencies were calculated using these data. The Au/C catalyst was the least active and the Pd/C catalysts were the most active for the formic acid decomposition reaction. At about 400 K, these Pd catalysts gave up to 0.04 moles of H₂ per minute per gram of Pd, with a selectivity of 95-99%. The H₂ selectivity for these catalysts was found to be only weakly dependent on the reaction temperature and the formic acid conversion. The Au/TiO₂ catalyst showed only a moderate selectivity to H₂ formation (<70%). The selectivity of this catalyst was improved considerably by the introduction of water vapour. This improvement derived from the high activity of the catalyst for the water-gas shift reaction.