Nanohybrid structured RuO/MnO/CNF as a catalyst for Na-O batteries.

A 3D RuO/MnO/carbon nanofiber (CNF) composite has been prepared in this study by a facile two step microwave synthesis, as a bi-functional electrocatalyst towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). RuO nanoparticles with the mean size of 1.57 nm are uniformly distributed on MnO nano-rods grown on electrospun CNFs. The electrocatalytic activity of the composites are investigated towards ORR/OER under alkaline condition. The ternary RuO/MnO/CNF composite showed superior ORR activity in terms of onset potential (0.95 V versus RHE) and Tafel slope (121 mV dec) compared to its RuO/CNF and MnO/CNF counterparts. In the case of OER, the RuO/MnO/CNF exhibited 0.34 V over-potential value measured at 10 mA cm and 52 mV dec Tafel slope which are lower than those of the other synthesized samples and as compared to state of the art RuO and IrO type materials. RuO/MnO/CNF also exhibited higher specific capacity (9352 mAh [Formula: see text]) than CNF (1395 mAh [Formula: see text]), MnO/CNF (3108 mAh [Formula: see text]) and RuO/CNF (4859 mAh g ) as the cathode material in Na-O battery, which indicates the validity of the results in non-aqueous medium. Taking the benefit of RuO and MnO synergistic effect, the decomposition of inevitable side products at the end of charge occurs at 3.838 V versus Na/Na by using RuO/MnO/CNF, which is 388 mV more cathodic compared with CNF.