Investigation of the porous nanostructured Cu/Ni/AuNi electrode for sodium borohydride electrooxidation

An electrochemical approach to nanostructured Cu/Ni/AuNi catalyst design using the electrodeposition process followed by galvanic replacement technique is presented. The procedure consisted of the electrodeposition of Ni–Zn on the Ni coating with subsequent replacement of the zinc by gold at open circuit potential in a gold containing alkaline solution. The surface morphologies and compositions of coatings were determined by energy dispersive X-ray and scanning electron microscopy techniques. The results showed that the Cu/Ni/AuNi coatings were porous composing of discrete Au nanoparticles. The electrocatalytic activity of Cu/Ni/AuNi electrodes for sodium borohydride electro-oxidation was studied using cyclic voltammetry, chronoamperometry, chronopotentiometry and electrochemical impedance spectroscopy techniques. The electro-oxidation current on Cu/Ni/AuNi catalyst is much higher than that on flat Au catalyst. The onset potential and peak potential on Cu/Ni/AuNi catalysts are more negative than that on flat Au catalyst for borohydride electrooxidation. The impedance behavior also shows different patterns, capacitive, and negative resistances and inductive loops at different applied anodic potentials. All results show that the Cu/Ni/AuNi catalysts can be applied as potential anode catalysts for the direct borohydride fuel cells.