(Digital Presentation) Electrochemical Synthesis of Chromium Carbide Coatings on the Surface of Carbon Fibres in NaCl-KCl-CrCl3-Cr Melt and Study of Their Electrocatalytic Properties
Authors: Gryaznov Artem , Slesarev Danil 
Published: December 2024

Composite materials based on carbides of refractory metals are of exceptional interest in various fields of application. They have unique characteristics such as high hardness, catalytic activity [1,2], etc. They are widely used in industry due to their high corrosion and oxidation resistance at high temperatures. Chromium carbide can be produced in various ways, for example, the most common method of production is physical deposition from the gas phase (PVD coating). Other synthesis methods are not so popular, but they are also widely known (electron beam surfacing, plasma arc welding, etc.). These methods have both advantages and disadvantages. Refractory metal carbide coatings obtained by electrochemical methods in molten salts have a number of advantages, such as the possibility of obtaining homogeneous coatings on products with complex shape, low porosity of coatings, high adhesion to the substrate.

Coatings of refractory metal carbides on a developed surface can also be used as electrocatalytic systems in reducing and oxidizing reactions. At the same time, the advantage of using electrocatalysis is the possibility of carrying out various reactions in a wide range of conditions from an extremely reducing environment to an extremely oxidizing one, the ability to control the route of the reaction by precisely adjusting the potential. Unlike common catalysis, electrocatalytic reactions do not leave reagents in the form of oxides, hydroxides or salts in the products. In electrochemical processes, an electron acts as a reducing agent, therefore high purity products are formed.

The purpose of this study was the electrochemical synthesis of chromium carbide in molten salts on a substrate made of carbon fibres Carbopon-B-22, as well as the study of electrocatalytic properties of the obtained composites.

To precipitate chromium onto a carbon substrate, a non-pressure transfer method in a molten equimolar mixture of NaCl and KCl containing 20 wt.% CrCl3, which is in contact with metallic chromium, was used. The synthesis of chromium carbides was carried out at temperatures of 1123 and 1223 K for 8-16 hours.

To study the kinetics of the electrocatalytic decomposition of hydrogen peroxide on the surface of carbon fiber–synthesized chromium carbides, a method based on measuring the volume of the released oxygen gas was used [3,4]. The initial carbon fiber Carbopon-B-22 was used as the cathode, and a carbon fiber electrode with Cr3C2 and Cr7C3 chromium carbides coatings was used as the anode.

In this study, two integral methods were used to determine the order of the hydrogen peroxide decomposition reaction: the substitution method (calculation of reaction rate constants according to equations for different reaction orders) and graphical (plotting of various concentration dependences on time and determining the linear dependence of one of them). The reaction rate constant was determined by the slope tangent of the straight line in the corresponding coordinates.

The activation energy of the process was calculated based on experimental data obtained at different temperatures.

References

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