Sustainable Electrochemical Conversion of Lignin to Renewable Chemicals with Simultaneous Hydrogen Production Via a Continuous Flow Electrochemical Reactor

Abstract

Lignin is the most abundant renewable source of aromatic compounds which can be utilized to generate fuels, chemicals, and polymers, however, due to the lack of an efficient lignin conversion process, it is usually burned as a low-grade fuel in the pulp and paper industry [1,2]. The key issue for commercial application of lignin is to develop an efficient depolymerization process to produce lower molecular weight aromatic compounds at relatively low cost. Several methods including photocatalytic degradation, hydrogenolysis, thermolysis, oxidation, biodegradation, and electrocatalytic degradation have been used to convert lignin to other value-added chemicals. Among them, electrochemical valorization of lignin is likely a promising method for commercial application due to occurring in moderate reaction conditions. Lead dioxide is one of the common active catalysts for electrochemical lignin oxidation [3]. However, due to the toxicity of lead which causes environmental and health issues, developing the lead-free electrocatalysts is greatly needed. Accordingly, we investigated the rate of lignin conversion and hydrogen production on different lead-free electrocatalysts developed in this study using a flow electrochemical reactor. Gas chromatography-mass spectrometry (GC-MS), high performance liquid chromatography (HPLC), and fourier transform infrared spectroscopy (FTIR) were employed to evaluate molecular weight distribution of lignin and characterize the functional groups.