Fluoride etched Ni-based electrodes as economic oxygen evolution electrocatalysts

• Published in: International journal of hydrogen energy 2022-01, Vol.47 (3), p.1613-1623
• Main Authors: Balaghi, S. Esmael, Heidari, Sima, Benamara, Mourad, Beyzavi, Hudson, Patzke, Greta R.
• Format: Article
• Language: English
• Subjects: Electrocatalysts; Fluoride; Metal etching; Nickel foam; Oxygen evolution reaction; Water oxidation
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2021.10.127

Electrochemical water splitting is a promising technology for eco-friendly energy storage. However, the design principles for highly active, robust, and noble metal-free electrocatalysts for industrial-scale hydrogen production remain controversial. Oxygen-free compounds containing anionic species with a very high oxidation potential, such as fluorides, have emerged as high-performance targets for thermodynamically stable oxygen evolution reaction (OER) catalysts. They can further be designed to fit the key criteria of high electrical conductivity and stability. Herein, we present a facile and scalable etching method for constructing fluoride doped metallic nickel-based anodes from industrial Ni foam sources with high application potential for large-scale hydrogen production setups. The fluoride-etched Ni-catalysts were investigated with a wide range of techniques, such as powder X-ray diffraction (PXRD), extended X-ray absorption fine structure spectroscopy (EXAFS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). Optimized catalysts displayed a promising overpotential of 220 mV for the OER at a current density of 60 mA cm−2, which is competitive with noble metal-based reference catalysts, such as iridium oxide. Electrochemical impedance spectroscopy (EIS) studies demonstrated that etching of the electrode surface in fluoride medium leads to a drastic decrease of Rct. The corresponding decreased resistivity towards electrochemical OER on the electrode surface gives rise to the notably enhanced performance, with a minimum of synthetic effort. [Display omitted] •One-step hydrothermal etching process to prepare porous NiFOOH on Ni foam.•Fluorine-modified electrodes exhibit superior activity in OER.•Promising overpotential of 188 mV for the OER at a current density of 10 mA cm−2.