Application of as-synthesized Co–Al layered double hydroxides for the preparation of the electroactive composites containing N-doped carbon nanotubes

A set of electrically conductive, porous and electrocatalytically active composites was prepared by catalytic chemical vapor deposition using Co–Al layered double hydroxides and acetonitrile. The effect of synthesis temperature, i.e. 600, 700 and 800 °C on their composition, structure and morphology was examined by means of X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, nitrogen sorption and scanning electron microscopy. Electrochemical properties of the composites were evaluated by cyclic voltammetry (CV) in alkaline solution in the presence and absence of oxygen. The composites were composed of metallic cobalt, metal oxides and turbostratic/graphitic carbon. Graphite-like carbon was doped with nitrogen (according to XPS analysis N concentration is 2 at.%) and occurred as multi-walled carbon nanotubes with diameters ranging from 10 up to 55 nm. The composites were a mixture of compounds showing strongly temperature-dependent crystallinity therefore they showed various specific surface areas (125, 114 and 53 m2 g− 1) and different specific capacitances (9, 7 and 3 F g− 1). The oxygen reduction peak in the CVs recorded in 0.1 M KOH was observed at − 0.26, − 0.28 and − 0.31 V versus Ag/AgCl/KClsat electrode for the samples prepared at 600, 700 and 800 °C, respectively.

► Co–Al LDHs are successfully used for the preparation of the electrocatalysts.
► A simple, inexpensive and efficient synthesis method is applied.
► N-doped multi-walled carbon nanotubes are grown on metallic cobalt at 600–800 °C.
► Synthesis temperature affects Co crystallite size and therefore CNT diameter.
► The composites are active in the oxygen reduction reaction in alkaline solution.