One-step electrodeposition of Co-Fe electrocatalysts with micro/nano-cauliflower like structure for highly efficient oxygen evolution reaction (OER)

In this study, Co-Fe coatings with different “Fe” contents were produced as catalysts for oxygen evolution reaction (OER) by a one-step electrodeposition method using 0–6 g/L FeSO4 in an electrolytic bath. The structure, electrochemical and electrical properties of the produced catalysts were carefully investigated. Scanning electron microscopy (SEM) results showed that the morphology of the prepared catalysts was varied with the “Fe” content. UV–vis diffuse reflectance spectroscopy (DRS) results along with Tauc plots indicated that the concentration of oxygen vacancy decreased by increasing the Fe content from 2 to 6 g/L, while the Co-Fe (2 g/L) catalyst with a band gap of 1.35 eV had the maximum concentrations of oxygen vacancies. Also, linear sweep voltammetry (LSV) results demonstrated that the Co-Fe (2 g/L) catalyst had the lowest overpotential (136 mV) at a current density of 10 mA.cm−2 and a small Tafel slope of 24.3 mV.dec− 1. The results confirmed the formation of the CoFe2O4 phase in the Co-Fe (2 g/L) catalysts. It was eventually concluded that the Co-Fe (2 g/L) catalyst with a nano-cauliflower like structure possesses the highest OER activity in 1 M KOH solution. [Display omitted] •The CoFe2O4 phase was formed in the Co-Fe (2 g/L) electrocatalyst.•Fe changed the morphology of the Co catalyst from conical to nanocauliflower-like.•The OER activity of the prepared Co-Fe samples was higher than that of the pure Co.•The prepared Co-Fe (2 g/L) electrocatalyst indicated the optimum OER activity.