Ethanol Oxidation on Electrocatalysts Obtainedby Spontaneous Deposition of Palladium onto Nickel-Zinc Materials

Ni-Zn and Ni-Zn-P alloys supported on Vulcan XC-72 are effective materials for the spontaneous deposition of palladium through redox transmetalation with PdIV salts. The materials obtained, Pd- (Ni-Zn)/C and Pd-(Ni-Zn-P)/C, have been characterized by a variety of techniques. The analytical and spectroscopic data show that the surface of Pd-(Ni-Zn)/C and Pd-(Ni-Zn-P)/C contain very small, highly dispersed, and highly crystalline palladium clusters as well as single palladium sites, likely stabilized by interaction with oxygen atoms from NiO moieties. As a reference material, a nanostructured Pd/C material was prepared by reduction of an aqueous solution of PdCl2/HCl with ethylene glycol in the resence of Vulcan XC-72. In Pd/C, the Pd particles are larger, less dispersed, and much less crystalline. Glassy carbon electrodes coated with the Pd-(Ni-Zn)/C and Pd-(Ni-Zn-P)/C materials, containing very low Pd loadings (22–25 mgcm2), were studied for the oxidation of ethanol in alkaline media in half cells and provided excellent results in terms of both specific current (as high as 3600 Ag(Pd)1 at room temperature) and onset potential (as low as 0.6 V vs Ag/AgCl/KClsat).