Carbon nanotube-based bimetallic nitride Co₃W₃N for electrocatalytic synthesis of ammonia under ambient condition

A kind of cheap carbon nanotube-based double transition metal nitrides Co₃W₃N/CNTs composite was prepared by hydrothermal and subsequent heat treatment under ammonia. By adjusting the proportion the of pre oxidation of CNTs and precursor CoWO₄ and ammonia heat treatment temperature, the Co₃W₃N in uniform load on the surface of the CNTs. Scanning electron microscopy (SEM) and transmission electron microscope (TEM) test results showed that the catalyst particles evenly dispersed on the surface of CNTs, due to oxidation CNTs for the good dispersion growth of precursor. The Co₃W₃N particle size on the CNTs was about 20 nm, which was significantly smaller than that of unsupported Co₃W₃N (100 nm). The electrochemical tests was carried out in a N₂ saturated 0.01 mol·L^-1 H₂SO₄ solution under different potential, and the material achieved the highest ammonia production rate and Faraday efficiency at -0.3 V, which reached approximately 12.73 μg·h^-1·cm^-2 and 13.59%, respectively. Under the same conditions, the ammonia production rate and Faraday efficiency of pure phase Co₃W₃N were only 1.08 μg · h^-1 · cm^-2 and 1.76%. The Co₃W₃N/CNTs sample showed excellent NRR (nitrogen reduction reaction) performance because of the Co₃W₃N as the active site and the synergistic effect of Co₃W₃N and CNTs.