Nickel-Copper-Carbon based electrocatalysts for oxygen evolution reaction: Sol-gel synthesis using chitosan

• Published in: International journal of hydrogen energy 2024-01, Vol.51, p.663-675
• Main Authors: Lima, Maria A.S., Raimundo, Rafael A., Araújo, Allan J.M., Oliveira, João F.G. de A., Loureiro, Francisco J.A., Macedo, Daniel A., Morales, Marco A.
• Format: Article
• Language: English
• Subjects: Chitosan; Electrocatalysts; Nickel-Copper-Carbon; Oxygen evolution reaction; Sol-gel synthesis
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2023.08.287

The development of highly efficient catalysts for oxygen (OER) and hydrogen (HER) evolution reactions are fundamental for the development of new sources of energy. To meet the global demand of energy, non-noble metal catalysts based on transition metals, in particular, Nickel (Ni) and Copper (Cu) metals are being widely explored and studied as promising candidates for electrocatalysts. Therefore, here we present: (a) the Sol-gel synthesis that uses chitosan as a polymerizing agent and subsequent reduction in H2 gas to synthesize carbon-coated NiCu nanoparticles, and (b) the microstructural and electrochemical evaluation of Ni95Cu5-C and Ni85Cu15-C samples. X-ray diffraction confirms the NiCu phase, while Raman spectroscopy confirms the presence of carbon. Field emission scanning electron microscopy shows nanoparticles with spherical morphology. From the electrochemical point of view, it was observed that the increase in copper content impairs the activity for oxygen evolution reaction when evaluated in 1.0 M KOH electrolyte. The Ni95Cu5-C electrocatalyst exhibited higher activity than Ni85Cu15-C, confirmed by low overpotential values (η = 319 mV vs. RHE) and Tafel slope (73 mV dec−1), and high values of CDL (4.1 mF cm−2), ECSA (102.5 cm2), SA (2.19 mA cm−2) and TOF (1.87 x10−4 mol O2 s−1). This work highlights a simple and inexpensive method to obtain Nickel-Copper-Carbon catalysts for application in water splitting in alkaline media. [Display omitted] •Nickel-Copper-Carbon was prepared by sol-gel methodology with subsequent reduction in H2.•Commercial chitosan biopolymer was used as polymerizing agent.•Electrochemical performance of samples is highly dependent on Nickel content.•Ni95Cu5-C showed excellent OER performance, with an overpotential of 319 mV vs. RHE at J = 10 mA cm−2.