Spinel Type Mn-Co Oxide Coated Carbon Fibers as Efficient Bifunctional Electrocatalysts for Zinc-Air Batteries

Mn-Co mixed oxide nanoparticles were coated onto carbon fibers (CFs) derived from asphaltene through a facile coating process. Homemade gas diffusion layers (GDLs) were prepared with the coated CFs to be employed as air electrodes and bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts for Zn-air batteries (ZAB). The Mn-Co oxide was identified as a cubic spinel phase (MnCo2O4) by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The composite air electrode showed excellent catalytic activity towards ORR/OER, outperforming the benchmark Pt-RuO2 catalyst in both half-cell and full-cell configurations with discharge/charge efficiencies of 63.7% and 60.0% at 10 and 20 mA cm(-2), respectively. After 200 cycles (100 h) at 10 mA cm(-2) the final efficiency of the composite electrode (58.9%) was still superior to that of Pt-Ru (43.2%).