Cobalt ferrite coated on Ti/Ni/PbOx with enhanced electrocatalytic stability for chloride ions-contained water splitting

Abstract

The advance of efficient, low-cost, and bifunctional catalysts for seawater splitting to produce hydrogen fuel is a challenge. However, by relying on transition metal-based compounds, a unique and attractive arrangement can be proposed. Here, a four-step process was used for the synthesis of the Ti/Ni/PbOx/CoFe2O4 electrocatalyst. First, thin films of nickel (by cathodic electrodeposition) and lead dioxide (by anodic electrodeposition) were synthesized on the activated titanium substrate. Then, using nitrate solution, CoFe coating with a thickness of ∼ 5 µm was applied. Finally, the coating is oxidized to form cobalt ferrite (CoFe2O4). The structure of the arrangement formed in each step was examined by X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (EDS) and the electrocatalytic performances were evaluated in 1 M KOH and 1 M KOH + 0.5 M NaCl solutions by electrochemical methods such as linear sweep voltammetry(LSV), electrochemical impedance spectroscopy (EIS), small amplitude cyclic voltammetry (SACV), accelerated chronopotentiometry (CP), and multi-step CP. The Ti/Ni/PbOx/CoFe2O4 electrode requires an overpotential less than 400 mV at 50 mA/cm2 with Tafel constant of 47.7 V/dec for OER. The results of the stability test in accelerated conditions and the alkaline solution containing chloride ions showed that the special arrangement of the cobalt ferrite electrocatalyst in this work improves its lifetime by more than 5 times compared to the normal cobalt ferrite. The synthesized Ti/Ni/PbOx/CoFe2O4 as a bifunctional electrode requires only a potential of 1.53 V at a current density of 10 mA/cm2 for overall seawater splitting. The dual-purpose properties of the Ti/Ni/PbOx/CoFe2O4 electrocatalyst can be considered for its wide use in the fields of sustainable and renewable energy.