Ni-based compounds in multiwalled graphitic shell for electrocatalytic oxygen evolution reactions

This study investigates Ni-based compounds (Ni, NiO, Ni3C) coated with a graphitic shell as electrocatalysts for the oxygen evolution reaction (OER). Electron paramagnetic resonance (EPR) and X-ray diffraction (XRD) are employed to identify the presence and contribution of Nickel ions (Ni0, Ni2+, Ni3+) and determine the phase composition. Electrochemical analyses, including overpotential, Tafel slope, electrocatalytic surface area (ECSA), and turnover frequency (TOF), assess the electrocatalytic activity. Notably, the catalyst exhibits an overpotential of 170.1 mV, a Tafel slope of 49 mV·dec-1, an ECSA of 964.7 cm2, and a TOF value of 52.8 s-1, surpassing RuO2. Furthermore, ex-situ studies elucidate the OER mechanism, revealing the formation of γ-NiOOH and β-NiOOH on the catalyst surface dominated by Ni3+ cations. The Raman spectra also suggest a graphitic "self-healing" phenomenon post-OER, attributed to the reduction of oxygen groups. The carbon shell serves a dual role, facilitating electron transfer and enhancing the dispersion of Ni nanocatalysts. Overall, our findings highlight the unique electrocatalytic properties of Ni-based compounds coated with a graphitic shell, offering insights into their potential as sustainable and high-performance OER catalysts. What is more, the proposed fabrication method for electroactive metal/carbon composites is general and was validated with an iron and iron/nickel mixture.The important informations such as samples description, instrumental techniques used during experiment and required softwares are included in README file.