Spatially dispersed one-dimensional carbon architecture on oxide framework for oxygen electrochemistry

Abstract The rational design of bifunctional electrocatalyst is important for sustainable energy storage and conversion devices such as metal-air batteries and fuel cells. Herein, we have designed a unique architecture where carbon nanotubes (CNTs) are supported on an oxide template. NiCo encapsulated N-doped carbon nanotubes were grown vertically outward from the nickel-cobalt oxide flowers for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The hybrid shows enhanced water oxidation performance (321 mV at 10 mA/cm2) and decent ORR activity (E1/2 at 0.75 V vs RHE) due to better conductivity and a large electrochemical surface area. Enhanced OER activity can be ascribed to high Ni and Ni3+ content whereas improved ORR activity results from enhanced active nitrogen species (pyridinic, M-Nx and graphitic) and higher water contact angle (due to unique architecture). Further, reversible oxygen electrochemistry with Δ E=0.80 V indicates its potential as a bifunctional electrocatalyst. The hybrid electrocatalyst has shown good operational stability and durability for OER and ORR. Finally, the practical feasibility as cathode catalyst for metal-air battery has been demonstrated by powering a light emitting diode.