Hydrogen production through NaBH_4 hydrolysis over supported Ru catalysts: An insight on the effect of the support and the ruthenium precursor

摘要

The NaBH_4 hydrolysis over Ru catalysts on different supports was here investigated. It was found that the support has a strong effect on the catalytic activity which was found to be in the order: Ru/activated carbon Ru/CeO_2 > Ru/TiO_2 > Ru/γ-Al_2O_3. On the most active system, namely Ru/activated carbon, the effect of the Ru loading and the metal precursor (RuCl_3 and Ru(NO)(NO_3)_3) was studied in more detail. Tests carried out with and without temperature control demonstrated that, for each precursor, the activity increases on increasing the Ru content. Moreover samples prepared by RuCl_3 were more active than the corresponding ones prepared by Ru(NO)(NO_3)_3. Characterization data, namely CO chemi-sorption and TEM analysis, point out that the Ru particles size is strongly affected from the Ru precursor used, Ru(NO)(NO_3)_3 resulting in very small Ru particles (diameter < 1 nm), RuCl_3 leading to Ru nanoparticles with average diameter of 2.4 nm. This latter size was found to be appropriate for the NaBH_4 hydrolysis reaction, which is proposed to be a structure sensitive reaction.