AN ELECTROCHEMICAL APPROACH TO NANOSTRUCTURED NI/PDNI CATALYST DESIGN USING THE ELECTRODEPOSITION PROCESS AND GALVANIC REPLACEMENT TECHNIQUE IS PRESENTED. THE PROCEDURE CONSISTED OF THE ELECTRODEPOSITION OF NI-ZN (TOP LAYER) ON THE NI (UNDER LAYER) COATING, WITH SUBSEQUENT REPLACEMENT OF THE ZINC BY PALLADIUM AT OPEN CIRCUIT IN A PALLADIUM CONTAINING ALKALINE SOLUTION. THE SURFACE MORPHOLOGIES AND COMPOSITIONS OF COATING BEFORE AND AFTER GALVANIC REPLACEMENT WERE DETERMINED BY ENERGY DISPERSIVE X-RAY AND SCANNING ELECTRON MICROSCOPY (SEM) TECHNIQUES. THE SEM RESULTS SHOWED THAT THE NI/PDNI COATINGS WERE POROUS, AND COMPOSED OF DISCRETE PD NANOPARTICLES WITH THE CRYSTALLITE SIZE OF ABOUT 58 NM. THE ELECTRO-CATALYTIC ACTIVITY OF NI/PDNI ELECTRODES TOWARD ELECTROOXIDATION OF ETHANOL WAS STUDIED BY USING CYCLIC VOLTAMMETRY AND ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY TECHNIQUES. THE RESULTS SHOWED THAT NI/PD-NI CATALYST HAD A HIGHER ELECTRO-CATALYTIC ACTIVITY FOR ETHANOL ELECTROOXIDATION THAN FLAT PD AND SMOOTH NI, RESPECTIVELY, DUE TO THE HIGH SURFACE ARE AND THE SYNERGISTIC EFFECTS OF PD AND NI. THEREFORE, THE NI/PD-NI CATALYSTS CAN BE POTENTIAL ANODE CATALYSTS FOR THE DIRECT ETHANOL FUEL CELL.

THE VSB-5 NANORODS WERE SYNTHESIZED BY CONVENTIONAL HEATING FOR 72 H IN THE PRESENCE OFTRIETHYLAMINE AS TEMPLATE.THEN, A NOVEL, CHEAP AND EFFICIENT CATALYST FOR ETHANOL ELECTROOXIDATION WAS DEVELOPED BY DECORATING NI2+IONS ON THE SURFACE OF MODIFIED CARBON PASTE ELECTRODE (CPE) WITH VSB-5 MOLECULAR SIEVES. THE ELECTROCHEMICAL ACTIVE SURFACE AREA OF THE MODIFIED ELECTRODE (NI-VSB-5/CPE) WAS CALCULATED BY CYCLIC VOLTAMMETRY (CV). ALSO, THE ELECTROCHEMICAL BEHAVIOR OF THE NI-VSB-5/CPE ELECTRODE TOWARDS THE ETHANOL OXIDATION WAS EVALUATED BY CV AS WELL AS CHRONOAMPEROMETRY METHODS. A SENSITIVE OXIDATION PEAK WAS OBSERVED AT 0.55 V IN 0.1 M NAOH SOLUTION FOR ELECTROCATALYTICOXIDATION OF ETHANOL WITH ECʹ MECHANISM. IT HAS BEEN OBSERVED THAT VSB-5 AT THE SURFACE OF CPE CAN IMPROVE CATALYTIC EFFICIENCY OF THE DISPERSED NICKEL IONS TOWARD OXIDATION OF ETHANOL. THE VALUES OF ELECTRON TRANSFER COEFFICIENT, THE MEAN VALUE OF CATALYTIC RATE CONSTANT AND DIFFUSION COEFFICIENT FOR ETHANOL AND REDOX SITES WERE OBTAINED TO BE 0.657, 1.80×105 CM3 MOL-1 S-1 AND 3.62×10-4 CM2 S-1, RESPECTIVELY.

NANOMATERIALS, AS A KIND OF NEW MATERIALS, EXHIBIT EXOTIC PHYSICAL AND CHEMICAL PROPERTIES DIFFERENT FROM CONVENTIONAL BULK MATERIALS BECAUSE OF THE SIZE EFFECT AND PRESENT A WIDE POTENTIAL APPLICATION IN MANY FIELDS. NICKEL HYDROXIDE WAS STUDIED FOR DECADES AND HAS ATTRACTED CONSIDERABLE ATTENTION IN DECADES DUE TO ITS DIREVSE APPLICATIOS, SUCH AS PRECURSORS FOR NICKEL CATALYSTS AND NICKEL OXIDES, THE ACTIVE MATERIAL IN THE POSITIVE ELECTRODE OF ALKALINE RECHARGEABLE BATTERIES, WHICH IS WIDELY USED AS A HYDROGENATION CATALYST, ACTIVE ELECTRODE MATERIALS FOR ALCOHOL OXIDATION [1- 3].