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