Upgrading Lignocellulose to Porous Graphene Enabled by Deep Eutectic Solvent Pretreatment: Insights into the Role of Lignin and Pseudo-lignin

Abstract

Converting lignocellulosic biomass into graphene-based materials in a cost-effective approach remains a grand challenge. This study tackled this challenge by implementing direct laser writing (DLW) to lignocellulosic biomass for synthesis of porous graphene (i.e., laser-induced graphene (LIG)). Deep eutectic solvents (DESs), including choline chloride:oxalic acid (ChCl:OA), choline chloride:formic acid (ChCl:FA), and choline chloride:ethylene glycol (ChCl:EG), were used to enable the fabrication of biomass-based films for DLW. It was found that the cellulose pulp resulting from the ChCl:OA pretreatment was a suitable substrate for LIG formation, requiring no surface treatment of the fabricated film prior to exposure to laser scribing. The obtained LIG had a 3D porous structure and high crystallinity. Pseudo-lignin present in the ChCl:OA pulp was proposed to contribute to the formation of LIG. Lignin in situ regenerated from the pretreatment slurry and redeposited onto the cellulose pulps can further promote the LIG formation on the cellulose pulp film (CPF). The LIG-embedded films were fabricated into on-chip supercapacitors (SCs) and dopamine sensors and further evaluated for electrochemical properties. All the devices showed good energy storage and electrochemical sensing performance, suggesting versatile applications of disposable and low-cost lignocellulose-derived electronics. Overall, the present work demonstrated a feasible and scalable photothermal route based on direct laser writing toward mass production of lignocellulose-derived porous graphene materials.

High lignin-containing nanocelluloses prepared via TEMPO-mediated oxidation and polyethylenimine functionalization for antioxidant and antibacterial applications

“…On the contrary, although catalyzed by the weak organic acid (i.e., oxalic acid), OA pretreatment led to the second highest removal of cellulose and hemicellulose, and a lignin increase as high as 12.41%, suggest signicant pseudo-lignin formation. 50,51 As the chemistry of pseudo-lignin is similar with genuine lignin and their characterization and separation were not comprehensively established, 49 pseudo-lignin was not specically distinguished from genuine lignin in LNCs production in the present work.…”

Evaluation of Gelation Time Affecting the Self-Assembled Framework of Lignin Nanoparticle-Based Carbon Aerogels and Their Electrochemical Performances

“…As shown in Figure b–d, the high-resolution C 1s spectra of the LRFC can be divided into five peaks, which involve C–C (sp 2 and sp 3 ) at 284.5 eV, C–N at 286.5 eV, C–O at 287.1 eV, and CO at 288.3 eV . The presence of significant amounts of C–O linkages in the LRFC can be attributed to oxygen-containing functional groups and interlinkages (e.g., −OH, C–O–C, and −COOH) in lignin . The high-resolution O 1s spectra (Figure e) are deconvoluted into three typical peaks representing −COOH at 534.2 eV, −O–CO at 533.1 eV, and C–OH at 532.3 eV .…”

“…25 The presence of significant amounts of C−O linkages in the LRFC can be attributed to oxygen-containing functional groups and interlinkages (e.g., −OH, C−O−C, and −COOH) in lignin. 26 The high-resolution O 1s spectra (Figure 4e) are deconvoluted into three typical peaks representing −COOH at 534.2 eV, −O−C�O at 533.1 eV, and C−OH at 532.3 eV. 27 These peaks arise from the oxygencontaining functional groups in lignin and RF.…”

Hydrothermal Treatment of Biomass Feedstocks for Sustainable Production of Chemicals, Fuels, and Materials: Progress and Perspectives

“…The green synthesis methods , have been explored for the production of biobased graphene using lignocellulosic biomass (e.g., wood) − and various types of wastes including agricultural wastes as a precursor. , Chen et al produced a few layers of graphene (2–10 atomic layers) from wheat straw using two-step processes (carbonization and graphitization) . The synthesized graphene was used in lithium-ion batteries as an anode material, and it shows high reversible capacity, superior rate capability, and good cycling performance.…”