(Invited) Insights and Strategies for Electrochemical Valorization of Lignin

Electrochemically driven organic reactions offer several advantages for the realization of abundant and inexpensive chemical feedstocks and fuels. In this presentation, advances in both oxidative and reductive transformations germane to the valorization of lignin are presented. First, a comprehensive description of the reactivity of electrochemically-generated PINO radicals for electrocatalytic oxidation of benzyl alcohols is reported. A combination of voltammetric, chronoamperometric, and computational results are shown that detail the proton-coupled electron transfer behavior of NHPI for the generation of PINO radicals. The dependence of the base used with NHPI is shown, with an optimal pKa for subsequent electrocatalytic oxidation of lignin cogeners. Second, the fragmentation of beta-O-4 linkages in lignin through electrochemical reduction pathways are discussed. Data are shown that suggest fragmentation is possible with selectivity at judiciously chosen reaction driving forces. Selectivity and conversion yields are shown for a variety of conditions, with an emphasis on aspects that pertain to the rate-limiting mechanistic aspects. Time permitting, efforts to couple these insights with photoelectrochemical systems will be discussed.