Cobalt Nanoparticles Modified Single-Walled Titanium Carbonitride Nanotube Derived from Solid-Solid Separation for Oxygen Reduction Reaction in Alkaline Solution

Titanium carbonitrides have promising catalytic properties for oxygen reduction reaction (ORR). However, its synthesis normally requires high temperatures (1200–1800 °C), thus limiting research carried-out on them. The catalytic properties of the carbonitrides have so far been improved through post-synthesis partial surface oxidation. This makes the entire process of making the desired catalyst cumbersome and complex. In this work, cobalt-modified single-walled titanium carbonitride nanotube (Co@TiC0.25N0.75) is synthesized via solvothermal method followed by solid-solid separation process. The problem of high temperature required for TiCN synthesis is successfully overcome, and a Co doping strategy is used to improve its catalytic performance. Different mass ratios of Co nanoparticles are loaded onto TiC0.25N0.75. It discovers that only a fraction of the Co dissolves at TiC0.25N0.75 lattice due to the solubility limit being ~ 0.98%. The remaining fraction of Co is found at the wall of the TiC0.25N0.75. The Co nanoparticles at the TiC0.25N0.75 wall complement the catalytic activity, while the dissolved Co at its lattice acts as active site modifier by increasing the proportion of Ti 2p3/2 in the low valence state. In alkaline solution, 10%Co@TiC0.25N0.75 shows appreciable ORR activity with onset and half-wave potential located at 0.85 and 0.73 V respectively; the performance is higher than that of TiN (0.69 and 0.55 V) and single-phase TiC0.25N0.75 (0.74 and 0.62 V). The results indicate that a charge transfer occurred between Co and TiC0.25N0.75 due to strong coupling effect. This gives a catalyst with appreciable ORR activity and stability.