Progress in Biomass Electro-Valorization for Paired Electrosynthesis of Valuable Chemicals and Fuels

Abstract

Environmental and energy concerns surrounding the use of fossil fuels are driving an increasingly rapid transition to sustainable and eco-responsible processes. Electrochemical processes can provide the necessary sustainability and economic roadmap for storing intermittent and renewable electricity by synthesizing, in cogeneration electrolyzers, energy carriers and/or synthetic chemicals (hydrogen, ammonia, etc.) via flagship reduction reactions (hydrogen evolution reaction (HER), nitrogen reduction reaction (NRR), etc.). To balance the electrochemical process, these cathodic processes have long been coupled to the oxygen evolution reaction (OER), which ultimately consumes almost 90% of the energy input. Recent years have witnessed an overwhelming development of anode scenarios based on biomass substrates, because OER cannot be driven below a certain potential threshold, while organics are thermodynamically more favorable. Therefore, paired electrolysis, which refers to cases where electrochemical oxidation and reduction are desired, embraces the electrocatalysis community for the electrolytic production of hydrogen, ammonia, etc. (cathode side), in parallel with value-added chemicals (anode side), all with a modest electricity input. The trade-off is selectivity at relevant current densities. This review discusses, the progress, challenges, and potential of biomass-fueled paired electrosynthesis of valuable chemicals and fuels. Fundamental principles, main biomass solubilization methods, and different scenarios for paired electrosynthesis are presented.