Core/shell Ni@Pd nanoparticles supported on MWCNTs at improved electrocatalytic performance for alcohol oxidation in alkaline media

Ni@Pd nanoparticles with core/shell structure uniformly dispersed on multi-walled carbon nanotubes (Ni@Pd/MWCNTs) is successfully prepared via a two-step strategy: impregnation–reduction method and replacement method. The Ni@Pd/MWCNTs composite was characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. It shows a uniform dispersion of Ni@Pd nanoparticles with core/shell structure on MWCNTs with the average particle size of 3.4 nm. The Ni@Pd/MWCNTs composite was used as electrocatalyst for alcohol oxidation in alkaline media for fuel cells. The electrocatalytic activity of ethanol oxidation on Ni@Pd/MWCNTs is 2.3 times higher than that of Pd/MWCNTs electrocatalyst at the same Pd loadings. The enhanced electrocatalytic properties could be attributed to not only the electric synergistic effect between Pd and Ni, but also the high use ratio of Pd for its shell structure.

► Nickel nanocrystals can be well-dispersed and deposited on carbon nanotubes (MWCNTs) by using chemical vapor deposition (CVD) method without adding other reducing agent.
► No other additives, Ni@Pd/MWCNTs nanosized catalysts can be synthesized by using replacement method.
► The electrocatalytic activity of ethanol oxidation on Ni@Pd/MWCNTs is 2.3 times higher than that of Pd/MWCNTs electrocatalyst.