Cobalt/nickel Nanofoams: Potential application in supercapacitors and OER/HER

Abstract

With the global energy crisis growing, the demand for alternative energy sources is more pressing than ever. Transition-metal nanofoams show great promise as materials for supercapacitors and electrocatalysts. However, their development in various fields is hindered by poor electrical conductivity and a lack of sufficient active sites. This study presents the successful synthesis of bi-metal (Cobalt and Nickel) nanofoams (CoNi-NF) using the hydrogen bubble template (DHBT) technique. The resulting foam-like structure exhibits a 3D porous architecture. The nanofoams' elemental composition was determined through EDX, confirming that each atomic percentages correspond to the Co/Ni ratio predetermined during synthesis. Cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) measurements were used to assess the electrochemical performance of the nanofoams before and after activation in 5 % H 2 O 2 . The bi-metal nanofoams showed higher specific capacitance values compared to the single metal nickel and cobalt nanofoams. The specific capacitance value of the oxidised nanofoam (CoNi-NF_75_OX) increased due to surface oxidation and activation by the 5 % H 2 O 2 chemical treatment, enhancing its capacitive response without degrading its morphology. The stability of CoNi-NF_75_OX nanofoam was good, maintaining its specific capacitance up to the 3000th cycle, which is a significant improvement over the as produced nanofoam (CoNi-NF_75). The electrochemical performance of cobalt-nickel, single cobalt foam and single nickel foam nanofoams was tested for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The high surface area of the nanofoams provides more active sites for the reaction, potentially enhancing electrocatalytic activity. Although the single Co nanofoam has a low overpotential (32 mV at 10 mA cm −2 ) for HER, it is less stable compared to the mixed nanofoams. This research provides valuable insights into the synthesis and characterisation of Co and Ni nanofoams and their potential as promising materials for use in electrochemical energy storage and conversion systems, specifically supercapacitors. • Bi-metal (Co/Ni) nanofoams were successfully synthesised using the DHB technique. • Specific capacitance increased with surface oxidation and activation with 5 % H 2 O 2 . • Multifunctional Cobalt/Nickel nanofoams: supercapacitor and OER/HER electrocatalyst.

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