Ni alloy nanowires for alkaline electrolysers

In recent years, the interest towards green hydrogen has drastically increased due to the global decarbonization process. Green hydrogen is obtained by water electrolysis using only electricity from renewable sources. It is considered one of the best storage systems in terms of environmental sustainability but not in economic ones. Nowadays, the research is focused on improving the Alkaline Water Electrolysis (AE) to reduce the cost of production. An approach to improve AE performance is based on nanostructured electrodes characterized by high electrocatalytic activity due to the very high surface area. In fact, the development of more efficient electrolysers with low-cost electrode-electrocatalyst materials can play a key role. The eligible materials must have some fundamental characteristics, such as good electrocatalytic properties, high conductivity, high availability, low cost, and good chemical stability. In alkaline environment it was demonstrated that, transition metals, and in particular Ni nanowires electrodes covered by different electrocatalyst, have good and stable performance. In this work, the attention was focused on the fabrication and characterization of nickel-alloy electrodes for both hydrogen and oxygen evolution reaction. Nanowires of Ni alloys were obtained by template electrosynthesis using polycarbonate membrane. Different alloys (Ni-Co, Ni-Zn, Ni-W and Ni-Fe) at different composition were studied in order to determine the most suitable alloy and its optimum composition. The electrodes have been studied morphologically and chemically through SEM, XRD, and EDS analyses. The composition of Ni-Co alloy appears very complex. It can be observed that the Co content is higher in the alloy than in the electrolyte. The same behavior can be observed in Ni-Fe alloy. In the case of the Ni-Zn alloy, its composition is linear with the composition of the bath. For Ni-W a very different trend was observed. Later, electrodes were tested both as anodes and as cathodes by CV, QSSP, and galvanostatic polarization in 30% w/w KOH solution. For hydrogen evolution reaction, the best alloy was the one rich in Co, followed by the alloy at 50% in Zn and Ni. For oxygen evolution reaction, the best performance was found in Ni-Fe alloy, in particular Fe 78.95. All the electrochemical tests show that nanostructured electrodes have a good chemical and mechanical stability. Preliminary results on the performance of an asymmetric electrolyzer consisting of Ni-Fe, for OER, and Ni-Co, for HER, nanostructured electrodes was also reported.