Combined electrochemical and spectroscopic investigations of carbonate-mediated water oxidation to peroxide

Highlights•Mechanism of two-electron water oxidation to peroxide investigated•Carbonate ions play a key role as a mediator in the reaction mechanism•Controlling near-surface carbonate concentration was key to enhancing performanceSummaryThe development of electrosynthetic technologies for H2O2 production is appealing from a sustainability perspective. The use of carbonate species as mediators in water oxidation to peroxide has emerged as a viable route to do so but still many questions remain about the mechanism that must be addressed. To this end, this work combines electrochemical and spectroscopic methods to investigate reaction pathways and factors influencing the efficiency of this reaction. Our results indicate that CO32− is the key species that undergoes electrochemical oxidation, prior to reacting with water away from the catalyst. Through spectroelectrochemical experiments, we noted that CO32− depletion is a factor that limits the selectivity of the process. In turn, we showed how the application of pulsed electrolysis can augment this, with an initial set of optimized parameters increasing the selectivity from 20% to 27%. In all, this work helps pave the way for future development of practical H2O2 electrosynthetic systems.Graphical abstract