Electrochemical Lignin Extraction from Lignocellulosic Biomass Residues for Producing Graphitic Carbon

Graphite is an energy-critical material essential for energy storage and electronics, but geographically concentrated production and rising demand have intensified the search for sustainable precursors for synthetic graphite manufacturing. Lignin, an abundant aromatic biopolymer, is a promising graphitic carbon precursor, but conventional extraction methods are energy-intensive and require substantial chemical inputs. Here, we introduce an integrated electrochemical platform that combines electrochemical alkaline peroxide delignification (EAPD) with electrochemical pH (EpH) swing to recover lignin from wheat straw (WS) and construction and demolition wood (CDW) under ambient conditions. The platform achieved lignin yields of ∼61 and ∼26% from WS and CDW, respectively, highlighting the influence of biomass type on process performance. Despite differences in yield, the recovered lignin samples exhibited physicochemical characteristics comparable across both feedstocks and to commercial standards, indicating that electrochemical extraction preserves lignin quality. Importantly, these lignin yields are comparable to those obtained with conventional APD using 1.5% v/v H2O2. The platform is inherently material-efficient because it eliminates externally supplied H2O2 and acids, resulting in a lower E-Factor, although further engineering optimization is needed to improve energy efficiency. The EAPD-extracted lignin was then converted into graphitic carbon via K2CO3-assisted Alkaline Thermal Graphitization (ATG), yielding graphitic carbon with an ID/IG ratio of 0.78 and lattice fringes with an interlayer spacing of 0.34 nm. Overall, this study demonstrates a reagent-minimized electrochemical platform for lignin extraction and its conversion into graphitic carbon, establishing a sustainable biomass-to-graphitic carbon pathway. Continued optimization of electrochemical delignification, graphitization conditions, and renewable electricity integration is expected to enhance the overall process sustainability further.