2019 Volume 52 Issue 5 Pages 423-429
For utilization of hydrogen carriers as a hydrogen source at a large scale, development of effective catalysts for hydrogen production is required. Though it is commonly accepted that the activity of catalysts can be enhanced by increasing the metal loading and reducing the metal particle size, the metal particle size is likely to increase with increased metal loading for catalysts prepared by the impregnation method. To obtain highly active catalysts that possess a high metal loading capacity and small metal particle size, we herein employed a preparation method for carbon-supported metal catalysts using ion-exchange resins. Three carbon-supported metal catalysts, Pd/C, Pt/C, and Ni/C, possessing high metal loadings (>10 wt%) and small metal particle sizes (2.7–3.6 nm from transmission electron microscopy (TEM) observations) were successfully prepared. The metal particle sizes estimated from CO or H2 pulsed chemisorption were larger than those observed by TEM, thus indicating that the small metal particles were embedded in the carbon support. Because of this embedding structure, the size of metal particles in the catalysts was retained at around 3 nm during carbonization at 500°C. Furthermore, dehydrogenation of formic acid was performed over the prepared catalysts at low temperatures. These catalysts exhibited high activity for hydrogen production from formic acid at temperatures in the range of 100–200°C. Pd/C and Pt/C yielded the highest turnover frequencies of 0.35 and 0.49 s−1, respectively, at 100°C, which was attributed to the large amount of small metal particles.
