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.