Green preparation of vanadium carbide through one-step molten salt electrolysis

Vanadium carbide (VC) as excellent ceramic and functional material is usually prepared by carbothermal reduction of V2O5 which must be extracted from a typical V slag by complex processes. Pollutants, such as ammonia-nitrogen wastewater, NH3 and CO2 are inevitably discharged. A novel and green method for VC preparation was proposed by one-step co-electrolysis of soluble NaVO3 and CO2 in molten salt. It was found that VC with high purity was easily obtained by reducing electrolysis temperature and CO2 flow rate to 600 degrees C and 10 mL min(-1) at 3.0 V. Besides VC with particles and layered stacking structure in products, a small amount of carbon and oxygen elements existed. The atomic percentage contents of C, V, and O elements in VC were about 50.0%, 44.5% and 3.8%, respectively. During electrolysis, CO32- and VO3- was reduced at about -0.55 V (vs. Ag/AgCl) and -1.38 V (vs. Ag/AgCl), respectively. CO32- ions were more easily reduced than V03, and was firstly reduced to CO32- and then converted to C. Then, VC was prepared by two routes from CO2 and NaVO3. One route is that VO3- ions are firstly electroreduced to VO2- ions and then are further electroreduced to VC with C. Another route is that VO3- ions are electroreduced to V which in-situ reacted with C to VC. Both VO3- and CO32- ions are electroreduced by two-step process. In final, VC is in-situ deposited on cathode. It provides a novel and green way to prepare VC and also achieves the high value-added utilization of vanadium slag and CO2.

Automated summary

High-purity vanadium carbide (VC) was successfully prepared by one-step co-electrolysis of NaVO3 and CO2 in molten salt, offering a novel and green method for the high value-added utilization of vanadium slag and CO2.