Co@N-CNTs derived from triple-role CoAl-layered double hydroxide as an efficient catalyst for oxygen reduction reaction

Co nanoparticle-encapsulated N-doped carbon nanotubes (Co@N-CNTs) are prepared as a Pt-free electrocatalyst for oxygen reduction reaction (ORR) via direct pyrolysis of a CoAl-layered double hydroxide (CoAl-LDH)/melamine mixture. The approach could bundle the following distinct features: (i) commercially available melamine as both carbon and nitrogen bi-functional sources; (ii) scalably prepared CoAl-LDH precursor chosen to play a triple role in catalyzing the formation of N-CNTs and serving the electroactive Co nanoparticles, as well as in facilitating the growth of long N-CNTs owing to the confinement effect of the non-active Al2O3 matrix formed; (iii) an alternative to prepare one-dimensional length-and-performance-tunable N-CNTs, which are obtained typically by using catalytic chemical vapor deposition (CCVD) of two gaseous carbon and nitrogen resources on the surface of an LDH layer. The long Co@N-CNTs exhibits the highly enhanced electrocatalytic activity and stability for ORR (onset potential at 929 mV, half-wave potential at 849 mV vs. RHE, and limited current density at 6.0 mA cm−2). The CoAl-LDH precursor-based approach may open up a simple and feasible alternative to design and produce low-cost electrocatalysts for fuel cells.