Development of a Pd-xCNT-Ni-yCB composite catalyst to enhance the oxidation of various alcohols in alkali mediums

Developing a comprehensive strategy and superior catalysts for alcohol oxidation is essential for real applications of direct alcohol fuel cells. By adding palladium (Pd) onto the nickel (Ni) nanoparticles loaded on a mixed multiwalled carbon nanotubes (CNTs) and carbon black (CB) support by a reduction method with 10 wt% Pd and 10 wt% Ni, various weight ratios carbon compositions of Pd-xCNT-Ni-yCB catalyst materials (x and y = 1–2) were also studied. Well-dispersed Pd nanoparticles with average particle sizes of 3.3 and 5.5 nm were present on the 1CNT-Ni-2CB and 1CNT-2CB composite supports, respectively. X-ray photoelectron spectroscopy (XPS) analysis indicated that Pd exhibits a metallic palladium surface state with some fraction of NiO and Ni(OH)₂ species. Alcohol oxidation e.g., methanol, ethanol, and iso-propanol in alkaline electrolytes was investigated by electrochemical measurements and analysis. Compared with single carbon catalysts, e.g., Pd-CNT and Pd-CB catalysts, in studies involving methanol, ethanol and isopropanol oxidation, most Pd-xCNT-Ni-yCB catalysts show high activity. The best performance obtained by Pd-1CNT-Ni-2CB could be related to the increased kinetics reaction and instantaneous presence of the bifunctional mechanism and electronic effect, resulting in a Pd and Ni alloy with a small amount of Ni(OH)₂ in the xCNT-Ni-yCB composite support surfaces.