Electrochemical Oxidation of Biomass for Solar Fuel Production

Abstract

Solar-to-chemical energy conversion, so-called artificial photosynthesis has received great attentions to address modern energy and environmental problems as it allows carbon-neutral production and the use of various chemical compounds, such as hydrogen, CO, and formate. Despite huge efforts made for decades, it still remains promising but premature for practical implementation due to low efficiency and stability of photosynthetic devices/materials. This is because of the slow and harsh water oxidation process, which can act as a rate-determining step for the overall reactions and lower the stability of photosynthetic devices. To address such problems, here, we report the coupling of photocatalytic reduction reactions for the synthesis of target chemicals with the electrochemical oxidation of biomass. By utilizing catalytic redox mediators, electrons were readily extracted from electrocatalytic oxidation and depolymerization of biomasses for electrochemical and photoelectrochemical hydrogen production. As a result, we could significantly reduce the oxidation potential for the extraction of electrons by several hundreds of mV and improve the performance of the devices in terms of kinetics and stability by employing biomass as a source of electrons instead of water. The catalytic redox mediators exhibited excellent stability in repeated biomass oxidation. We believe that the present study can provide insights for design and fabrication of artificial photosynthetic devices for practical application.