Synthesis and study of palladium colloids and related catalysts

Abstract Colloidal palladium particles were prepared by reduction with hydrogen of H 2 PdCl 4 in a mixture of H 2 O, trioctylamine (TOA), and cyclohexane. According to 14 N NMR, 35 Cl NMR and EXAFS data, the reduction of Pd was found to proceed under an auto-catalyzed regime via (HTOA) 2 [PdCl 4 ] complex formation. After complete reduction of Pd(II) (1 mol H 2 consumed per 1 Pd atom), H 2 consumption abruptly changed to 0.7 H 2 mol per 1 Pd atom. Unusually large amounts of H 2 adsorbed per Pd-atom could be due to the formation of palladium hydride by highly dispersed and defected Pd particles. TEM shows that Pd particles in catalysts obtained by metal particles deposition on carbon material Sibunit look like “hedgehogs” with needles 100 A long and 20–40 A in diameter.