Nanostructured Ru-doped Co3O4 as an efficient electrocatalyst for oxygen reduction reaction in alkaline medium

Ru-doped Co3O4 (RuxCo3-xO4, 0.1 ≤ x ≤ 0.3) catalysts are prepared by co-precipitation method. The prepared powders are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), transmission electron microscope (TEM), inductively coupled plasma-optical emission spectrometry (ICP-OES), Brunauer-Emmett-Teller (BET) test and X-ray photoelectron spectroscopy (XPS). These characterization methods confirm that the crystal structure of RuxCo3-xO4 is consistent with that of Co3O4, and the catalyst powders are in the form of nanoparticles with an average particle diameter of about 20 nm. The electrochemical performances of the catalysts are evaluated by cyclic voltammograms and linear sweep voltammograms in 0.1 M KOH solution. When x = 0.2, RuxCo3-xO4 shows the best electrochemical performances with the onset potential (Eonset) at 0.88 V, the half-wave potential (E1/2) at 0.77 V and the limited current density at 4.41 mA cm−2. The oxygen reduction reaction for RuxCo3-xO4 mainly follows four-electron pathway with the electron transfer number at about 3.5. Furthermore, Ru0.2Co2.8O4 has greater stability and anti-methanol property than Pt/C. These results revealed that RuxCo3-xO4 is an oxygen reduction catalyst with high performance and low cost.