MnxIr1−xO2/C used as bifunctional electrocatalyst in alkaline medium

There is a growing interest in oxygen electrochemistry as conversions between O₂ and H₂O play an important role in a variety of renewable energy technologies. In this paper, bifunctional electrocatalysts of the general formula Mn_xIr_1-xO₂/C were prepared using a pyrolysis method. Their physical characteristics were examined via transmission electron microscopy, and the electrochemical properties were examined via cyclic voltammetry and linear sweep voltammetry measurements in 1M KOH solution. Experimental results show that with the content of iridium increasing in Mn_xIr_1-xO₂/C, the oxygen reduction reaction (ORR) activity first increases and then decreases. Mn_0.75Ir_0.25O₂/C has the highest ORR activity and its half-wave potential obtains -0.071V (relative to Hg/HgO electrode). It is worth noting that doping the MnO₂/C nanoparticles with only a small amount of iridium can considerably improve the oxygen evolution reaction (OER) activity of MnO₂ in the alkaline medium. The oxygen evolution current density at 0.75 V vs. Hg/HgO of Mn_0.75Ir_0.25O₂/C was nearly 4.31 times as that of MnO₂/C. The results offer an important direction for the development of bifunctional oxygen catalysts in alkaline medium.