Synthesis of Refractory Metal Carbides on Carbon Fibers in Molten Salts and Their Electrochemical and Electrocatalytic Properties

Abstract

Method of currentless transfer in molten salts was used for synthesis of tantalum and niobium carbides coatings and crystals of molybdenum carbide on carbon fibers. Temperature of process was varied from 800 up to 900 °C, and time of process from 0.5 up to 24 hours. Figure 1. Micrographs of carbon fiber with TaC and NbC coatings and Mo2C crystals (from left to right), obtained in molten salts melts by currentless transfer. The splicing of fibers with each other was not observed; coatings were uniform in a cross section as well as along the fiber. Thickness of TaC and NbC coatings on carbon fiber was 50 – 250 nm. Size of crystals of Mo2C was approximately several micrometers. Investigation of refractory metal (Ta, Nb, Mo) carbides on carbon fiber of the Carbopon-B-22 brand was carried out by impedance spectroscopy method. The values of the standard rate constants of charge transfer and capacities of the double electric layer were determined for synthesized materials in water solution with hydrogen peroxide. Coatings and crystals of refractory metal carbides on carbon fibers can be used as catalysts and electrocatalysts. The kinetics of the electrocatalytic decomposition of hydrogen peroxide on the surface of TaC/C, NbC/C and Mo2C/C composite materials was studied. This reaction was investigated on measuring the volume of released oxygen. The initial carbon fiber of the Carbopon-B-22 brand was used as the cathode. The composite materials made of carbon fiber coated with tantalum carbide TaC (NbC) or modified by molybdenum carbide Mo2C served as the anode. The reaction order was established, the rate constants and activation energies of the hydrogen peroxide decomposition were calculated. The composition with the highest electrocatalytic activity was determined. Figure 1