Ni alloy nanowires as high efficiency electrode materialsnfor alkaline electrolysers

Abstract

Hydrogen production by water electrolysis (WE) is a very promising technology because it is a pollution-free process especially if renewable sources are employed to energy supply. Nowadays, the cost of hydrogen production by WE is higher than other available technologies, which makes WE not competitive. Many efforts have been made to improve WE performance, through the use of electrodes made of transition metal alloys as cathode and compound of metal oxide as anode [1]. In the field of water-alkaline electrolyzer, the development of cheap nanoporous based nickel electrodes with high electrocatalytic features is one of the potential approaches to increase the WE performance [2]. A facile method for obtaining nanostructured electrodes is template electrosynthesis. Through this method, we have fabricated electrodes formed of Ni nanowires and its alloys that have a very high surface area. In previous works, we have shown that water-alkaline electrolyzer with Ni nanowires electrodes covered by nanoparticles of IrO2 as an anode and Pd as a cathode have good and stable performance also at room temperature [2-5]. In this work, the attention has been focused on the fabrication of nickel-alloy electrodes. Three different alloys (Ni-Co, Ni-Zn and Ni-W) at different composition were studied in order to found the best alloy and relative best composition. Nanostructured electrodes were obtained by template electrodeposition using a nanoporous membrane and starting from aqueous solutions containing the two elements of the alloy at different concentrations. We found that composition of alloys can be tuned by electrolyte composition and also depends on the difference on the redox potential of elements and on the presence of complexing agents in deposition bath. The chemical and morphological features of these nanostructured electrodes will be presented and discussed. Furthermore, electrochemical and electrocatalytic tests aimed to establishing the best alloy composition were carried out for both hydrogen and oxygen evolution reaction. Then, test conducted at a constant current density in aqueous solution of potassium hydroxide (30% w/w) will be also reported. For all investigated alloys we have obtained very encouraging results.