Cubic spinel cobalt oxide/multi-walled carbon nanotube composites as an efficient bifunctionalelectrocatalyst for oxygen reaction

A facile hydrothermal route has been adopted to fabricate cubic spinel cobalt oxide/multi-walled carbon nanotube composite using acid-functionalized carbon nanotubes as structure directing/oxidizing agents. The composite material demonstrated excellent bifunctionality before and after long periods of cyclic voltammetry cycling. After cycling, the oxygen reduction current density of the composite shows about 4, 34 and 3 times improvements in comparison to multi-walled carbon nanotube, cubic spinel cobalt oxide and their physical mixture, respectively. The oxygen evolution current density of the composite was 49% higher than the physical mixture and even greater than each component alone after 500 CV cycles. The cause of high performance is presumably contributed to the synergistic coupling effects between the multi-walled carbon nanotubes and the cubic spinel cobalt oxide.