Electrocatalysis of carbon black- or chitosan-functionalized activated carbon nanotubes-supported Pd with a small amount of La2O3 towards methanol oxidation in alkaline media

The Pd/C catalysts with and without a small amount of La₂O₃ were synthesized by a simple reduction reaction with sodium borohydride in aqueous solution. The structure and morphology of these catalysts were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy and transmission electron microscopy. The electrocatalytic performance of these catalysts for methanol oxidation in alkaline media was investigated using cyclic voltammetry, chronoamperometry and CO stripping experiments. The results show that the Pd–La₂O₃/C catalyst has a higher catalytic activity than the Pd/C catalyst, but the effect of La₂O₃ cannot be explained by a bi-functional mechanism. X-Ray photoelectron spectroscopy analyses suggest that the higher content of metallic Pd caused by the addition of La₂O₃ contributes to the better catalytic activity of Pd–La₂O₃/C. Based on the good electrocatalytic performance of Pd–La₂O₃/C, the Pd–La₂O₃ catalyst supported on chitosan (CS)-functionalized activated carbon nanotubes was prepared, and it exhibited a better catalytic activity. The improvement is attributed to the good dispersion status of metal particles and the further increase of metallic Pd due to the presence of CS.