Kinetics and oxidation pathways of Fe3+-catalyzed carbon-assisted water electrolysis for hydrogen production

Carbon-assisted water electrolysis can significantly reduce the electricity consumption of electrolytic hydrogen production, but its slow kinetics limit its further development. In-depth investigation of the oxidation pathways and control steps of coal particles during electrolysis can help to improve the reaction rate in a more targeted manner. In this study, the electrochemical activities of several different ranks of coal, activated carbon, and graphite are compared, and the electrooxidation process is disentangled to investigate the kinetic characteristics of the oxidation of solution catalysts, the reaction of coal with solution catalysts and the electrooxidation of coal. Structural characterization is used to investigate the key factors affecting the electrochemical activity. The results show that coal particles mainly undergo indirect oxidation during electrolysis, and direct oxidation only accounts for a small fraction of oxidation; the oxidation of the solution catalyst on the electrode surface is reversible, and the controlling step in the whole process is the redox reaction between the solution catalyst and coal particles. A variety of oxygen-containing functional groups are generated on the surface of coal particles after electrolysis, among which the C-O group plays a more critical role in the oxidation activity. • For the first time, the kinetics of CAWE was studied in detail by splitting. • Direct evidence that coal particles mainly undergo indirect oxidation was obtained. • The oxidation of coal particles clearly has two phases. • The accuracy of Fe 2+ concentration detection in flat electrodes is relatively high.