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RESEARCH ARTICLE

Nickel oxide on directly grown carbon nanofibers for energy storage applications Abraham Gomez Vidales1   · Deepak Sridhar1   · Jean‑Luc Meunier1 · Sasha Omanovic1 Received: 27 March 2020 / Accepted: 17 August 2020 © Springer Nature B.V. 2020

Abstract Nickel oxide on directly grown carbon nanofibers (CNF-NiO) electrodes were fabricated and used as cathodes for hydrogen production by water electrolysis and as electrode materials for supercapacitors. Tafel polarization from the CNF-NiO electrodes showed an improvement in the hydrogen evolution reaction. This was attributed to the increment of the electrochemically active surface area, conductivity, and the synergy effects between the nickel oxide, carbon nanofibers, and nickel foam substrate. When used for supercapacitor applications, these electrodes showed a specific capacitance of ca. 776.20 ± 26 mF ­cm−2 at a current density 3 mA c­ m−2. These electrodes prepared using a facile method also exhibited a capacitance retention of 89% even after 3000 cycles with a coulombic efficiency of 89% when cycled at 20 mA c­ m−2. Considering the simplistic approach of the electrode preparation, the stability, and the capacitance, this method opens an avenue to try various metal oxide deposit on the directly grown CNF template. Graphical abstract Precursor coats (Ni)

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Abraham Gomez Vidales and Deepak Sridhar contributed equally to this work. Electronic supplementary material  The online version of this article (https​://doi.org/10.1007/s1080​0-020-01471​-8) contains supplementary material, which is available to authorized users. Extended author information available on the last page of the article

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Journal of Applied Electrochemistry

Keywords  Carbon nanofibers · Hydrogen · Metal oxides · Supercapacitors · Water electrolysis

1 Introduction According to the Intergovernmental Panel on Climate Change (IPCC), since the industrial revolution, global warming is rapidly increasing, and the record set of temperatures reached in the last 25 years is tangible proof of this [1]. The dependence on fossil energies results in emissions of greenhouse gases, with carbon dioxide ­(CO2) (80% of the contribution) as the product of combustion. As global energy demand continues to grow, ­CO2 emissions are expected to rise by 1.3% annually; consequently, the use of fossil fuels for energy needs will increase, resulting in critical environmental problems in the world. In the same context, fossil fuels are rapidly being depleted. The most optimistic estimates show that there are oil reserves for another 100 year