Structure, functional composition and electrochemical properties of nitrogen-doped multi-walled carbon nanotubes synthesized using Co–Mo, Ni–Mo and Fe–Mo catalysts

Abstract

We studied the effect of Co–Mo/MgO, Ni–Mo/MgO, and Fe–Mo/MgO catalysts on the structure and functional composition of nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) synthesized by chemical vapor deposition method. Polyoxomolybdates containing Co–Mo, Ni–Mo, Fe–Mo сores were used as the catalyst precursors and acetonitrile was the source of carbon and nitrogen for the growth of N-MWCNTs in argon atmosphere at 900 °C. The Ni–Mo/MgO catalyst promoted the formation of N-MWCNTs with the smallest outer diameter of 8 nm and the highest content of embedded nitrogen of 2.7 at.% with a predominance of pyridinic nitrogen form. Co–Mo/MgO and Fe–Mo/MgO catalysts yielded thicker N-MWCNTs with an average outer dimeters of 12 and 15 nm and lower nitrogen content of 2 and 1.5 at.%, respectively. N-MWCNTs were tested as electrodes in electrochemical capacitors and Li-ion batteries. A higher efficiency of the N-MWCNTs synthesized using Ni–Mo/MgO catalyst confirmed the advantage provided by a high content of nitrogen in the nanotube walls.