Electrocatalytic properties of in situ-generated palladium nanoparticle assemblies towards oxidation of multi-carbon alcohols and polyalcohols

Two-dimensional assemblies of palladium nanoparticles (PdNPs) were generated by in situ reduction of [PdCl4]2− ions bound on polyethylenimine silane-functionalized silicon and indium tin oxide (ITO)-coated glass surfaces. Atomic force microscopy imaging indicates an average PdNPs size of 8.4 ± 2.6 nm and confirms a uniform generation of these assemblies on the silicon surface. Ultraviolet–visible spectroscopy, surface zeta potential measurements and impedance spectroscopy were used to follow the changes in surface species and corresponding variation in surface charge during different steps of the synthesis of the PdNPs. These assemblies generated on a functionalized ITO surface are effective catalysts for the reduction of 4-nitrophenol to 4-aminophenol in the presence of excess sodium borohydride and follow pseudo-first-order reaction kinetics with an apparent rate constant (kapp) of 5.99 × 10−4 s−1. Finally, the electrocatalytic behavior of these PdNPs assemblies in alkaline medium was evaluated for oxidation of the multi-carbon alcohols ethanol, n-propanol and isopropanol as well as for the polyalcohols ethylene glycol and glycerol. Analysis of cyclic voltammetric response reveals that PdNPs assemblies are effective electrocatalysts for isopropanol oxidation and demonstrate superior performance for the oxidation of both polyalcohols, with high tolerance against accumulation of carbonaceous species on the electrode surface.