Volume-based electrodes for enhancing limiting currents in electrochemical conversion reactions

Abstract

The negative environmental effects of large-scale use of fossil fuels, chemicals, and energy-intensive processes are forcing us to develop green alternatives to mitigate the climate crisis. Electrochemistry, powered by renewable energy, provides us with a direct way to produce precursors or materials from green electricity and benign reagents such as water, carbon dioxide (CO2), or oxygen. A widely known example is water electrolysis to produce hydrogen as a green fuel and chemical building blocks for other chemicals. Alternatively, CO2 can be fed to an electrolyzer to produce sustainable carbon-based materials - such as pharmaceuticals, paints, and synthetic fuels - that are otherwise obtained from fossil fuels. Electrochemistry is therefore a versatile and promising technology that could provide a strong foundation for sustainable alternatives to various environmentally unfriendly processes.
Because electrochemical systems are often studied as replacements for well-established and optimized industrial processes, the benchmarks to achieve an economically viable and competitive status are high. Most importantly, the processes must be efficient with materials and energy,
resulting in requirements such as high current density, energy efficiency and product selectivity. These are hampered in many systems by poor solubility of reagents in water, such as the aforementioned CO2 and oxygen. The low reagent concentration results in reagent depletion, intensified competition with parasitic side reactions, and low selectivity at industrially relevant current densities. Such systems are severely limited by the slow mass transport and availability of reagents towards and at the electrode surface.