Oxidative Depolymerisation of Kraft Lignin: From Fabrication of Multi-Metal-Modified Electrodes For Vanillin Electrogeneration via Pulse Electrolysis To High-Throughput Screening of Multi-Metal Composites

The production of green hydrogen may be greatly aided by the use of an alternative anode reaction replacing oxygen evolution to increase energy efficiency and concomitantly generate value-added products. Lignin, a major component of plant matter, is accumulated in large amounts in the pulp and paper industry as waste. It has excellent potential as a source of aromatic compounds and can be transformed into the much more valuable aroma chemical vanillin by electrochemical depolymerisation. We used a flow-through model electrolyser to evaluate electrocatalyst-modified Ni foam electrodes prepared by a scalable spray-polymer preparation method for oxidative lignin depolymerisation. We demonstrate how pulsing, i. e. continuously cycling between a lower and a higher applied current, increases the amount of formed vanillin while improving the energy efficiency. Further, we present a scanning droplet cell-assisted high-throughput screening approach to discover suitable catalyst materials for lignin electrooxidation considering that a suitable electrocatalyst should exhibit high activity for lignin depolymerization and simultaneously a low activity for vanillin oxidation and oxygen evolution. Combining electrosynthesis and electrocatalysis can aid in developing new customised materials for electrochemical processes of potential industrial interest. Electrocatalytic lignin oxidation: Valorisation of biomass as an alternative anode reaction in water electrolysis can mitigate energy costs by value-added product generation. The targeted lignin oxidation to vanillin suffers from parasitic reactions such as oxygen evolution and vanillin oxidation. Here, pulse electrolysis and scanning droplet cell-assisted performance screening are presented as methods to aid the search for active anodes and prevent overoxidation.image

Automated summary

This article discusses the potential of using an alternative anode reaction to produce green hydrogen and convert lignin into valuable chemicals. The use of pulse electrolysis and scanning droplet cell-assisted screening are explored as methods to enhance the efficiency and selectivity of the electrochemical processes.