RESUMEN
The 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.
RESUMEN
Molecular catalysts and their assemblies are important model systems in electrocatalysis. This is largely because their active sites, secondary coordination spheres, and reaction environments can be rationally modulated. Such experiments yield important insights into the structure-activity relationships that can be used to design improved catalysts or translated to more technologically mature systems. However, in the context of electrocatalysis, molecular catalysts are often dissolved in an electrolyte or heterogenized on an electrode that is completely submersed in an electrolyte (e.g. H-cell) or reaction setups that are not used in practical systems and use poorly soluble gaseous reactants like CO2, CO, or O2. This is beginning to change, with a growing emphasis being placed on investigating molecular catalysts and catalytic assemblies (e.g. metal/covalent organic frameworks and polymers with molecular active sites) in gas-diffusion electrodes (GDEs) that feed the reactant directly from the gas phase to the catalytic sites and enable industrially viable current densities. Against this backdrop, this perspective first details the emerging set of molecular catalyst-embedded GDE-based systems and what the community has learned thus far from these efforts. We next identify the gaps in knowledge and performance that are yet to be closed and offer strategies for exploring in this direction. Finally, we conclude with a forward-looking discussion that highlights several new avenues to be pursued with molecule-based GDE platforms and how this can accelerate progress in the electrocatalysis field as a whole.
