Boosting electrocatalysis of oxygen reduction and evolution reactions with cost-effective cobalt and nitrogen-doped carbons prepared by simple carbonization of ionic liquids

Abstract

Development of cost-effective, bi-functional carbon electrocatalysts via direct carbonization of ionic liquids (bis(cholinium) tetrachlorocobaltate(II) ([Ch]2[CoCl4]) and bis(1-butyl-3-methylimidazolium) tetrachlorocobaltate(II) ([Bmim]2[CoCl4])) is reported herein for the first time. Carbon electrocatalysts, dual-doped with cobalt and nitrogen, were tested for oxygen reduction (ORR) and oxygen evolution (OER) reactions. Both materials show high bi-functional catalytic activity and excellent stability due to synergistic effects arising from the presence of nitrogen and cobalt. Electrocatalyst prepared by carbonization of [Ch]2[CoCl4] show exceptional activity and selectivity toward ORR. Conversely, electrocatalyst prepared from [Bmim]2[CoCl4] showed a slightly better OER performance indicating that different catalytic sites are responsible for O2 reduction and H2O oxidation. Parent CoO particles with graphitic nitrogen boost activity for ORR, while elemental Co supported by nitrogen atoms is responsible for OER activity. Finally, energy consumption during electrolytic oxygen production was calculated revealing energy saving when using two materials as anode electrocatalysts.