In Situ Lignin Sulfonation for Highly Conductive Wood/Polypyrrole Porous Composites

Abstract

features low-cost, low-toxicity, and pseudocapacitive behavior, and can be produced by aqueous synthetic chemical routes. [2] The conductivity of PPy is derived from the conjugated double bonds in its backbone and can reach up to 100 S cm −1 after oxidation. [3] PPy has already been used in conjunction with wood or wood-derived materials for the production of green electronics and electrochemical devices. [4] Through the bottom-up approach, pyrrole has been polymerized on cellulosic materials such as nanocellulose, [5] Kraft pulp fibers, [6] Cladophora-derived cellulose, [7] and cellulose filter paper. [8] The lightweight nanocellulose/PPy composites showed flexibility and good mechanical performance with high charge capacities and charging rates for application as paperbased batteries. In addition, charged sulfonic groups of lignosulfonates can act as counterions for PPy, stabilizing positive charges of PPy, and remain trapped within PPy structure. [9] Lignosulfonates have therefore been used in addition to polypyrrole during polymerization as anionic additives and dopants, [10] providing increased conductivity as well as thermooxidative and moisture stability. To use the redox capacity in lignin, pyrrole has been electrochemically polymerized at Au electrodes in aqueous lignosulfonate solutions to create an interpenetrating network of a polymer composite that can be used for charge and energy storage. [11] Lignosulfonates have also been introduced into cellulose nanofibers/poly(3,4-ethylenedioxythiophene) (PEDOT) paper supercapacitors to increase the specific capacitance and the areal capacitance. [12] To address the rising need of sustainable solutions in electronic devices, the development of electronically conductive composites based on lightweight but mechanically strong wood structures is highly desirable. Here, a facile approach for the fabrication of highly conductive wood/polypyrrole composites through top-down modification of native lignin followed by polymerization of pyrrole in wood cell wall. By sodium sulfite treatment under neutral condition, sulfonated wood veneers with increased porosity but well-preserved cell wall structure containing native lignin and lignosulfonates are obtained. The wood structure has a content of sulfonic groups up to 343 µmol g −1 owing to in situ sulfonated lignin which facilitates subsequent oxidative polymerization of pyrrole, achieving a weight gain of polypyrrole as high as 35 wt%. The lignosulfonates in the wood structure act as dopant and stabilizer for the synthesized polypyrrole. The composite reaches a high conductivity of 186 S m −1 and a specific pseudocapacitance of 1.71 F cm −2 at the current density of 8.0 mA cm −2 . These results indicate that tailoring the wood/polymer interface in the cell wall and activating the redox activity of native lignin by sulfonation are important strategies for the fabrication of porous and lightweight wood/conductive polymer composites with potential for sustainable energy applications.

Aqueous Processable One-Dimensional Polypyrrole Nanostructured by Lignocellulose Nanofibril: A Conductive Interfacing Biomaterial

“…We summarized various cellulose-based conductive platforms as reported in the literature in Table . The obtained electrical conductivity of the vacuum-filtered membrane of 12PPy@LCNF is higher than what was reported for composites of nanocellose/PPy or nanocellulose/reduced graphene oxide (rGO). , In some studies, the monolith fabrication was carried out through in situ polymerization of pyrrole within the paper substrate or wood tissue, which restricted the processability. ,, In this perspective, the facileness to process PPy@LCNFs as various solid forms is advantageous in adapting versatile scenarios in building bioelectronic interfaces and devices. It is worth noting that the protonation level of PPy strongly depends on the experimental conditions of its preparation.…”

“…This redox couple potentially permits electronic interactions between lignin and the electrochemically active material, thus enabling reversible charge-transfer in an integrated system. Several reports have also confirmed that lignin effectively enhances the capacitance of pseudocapacitive polymers, including PPy. − As another thread, the complexation of lignin with Fe­(III) ions is well-documented and has been integrated in the design strategy for processing lignin-containing or lignin-derived functional materials. − Inspired by the use of azo-dye to form a complex with Fe­(III) ion as a soft template to guide the synthesis of 1D pristine PPy, we came up with the approach to use LCNF as the PPy morphology modulating hard template that we described here (Scheme ). As lignin is preserved on the fibril surface, we hypothesize that it acts as immobilization domains for Fe­(III) ions and consequently confines the polymerization of pyrrole by providing nucleation sites on the fibril surface, respectively.…”

High-Strength and UV-Shielding Transparent Thin Films from Hot-Pressed Sulfonated Wood

“…The sulfonated pine wood veneers were prepared according to the protocol reported previously . In brief, 2.5 g of pine veneers was wetted in deionized water and subsequently sealed in an acid digestion vessel (45 mL, Parr Instruments) containing 40 mL of a 0.7 M Na 2 SO 3 solution at pH 7 (adjusted with H 2 SO 4 ).…”

“…In our previous work, we have developed a facile in situ lignin sulfonation process under subcritical conditions for the fabrication of conductive wood composites with polymers such as poly­(3,4-ethylenedioxythiophene) (PEDOT):poly­(styrene sulfonate) (PSS) and polypyrrole. , In this work, transparent thin wood films were prepared from sulfonated pine veneers by densification using hot pressing. The preserved lignin and lignosulfonates in wood structure were exploited as a natural binder and UV-blocking material.…”

B, N Co-doped Wood Scrap Charcoal for High Supercapacitor with Decorated Conductivity

“…The former is pseudocapacitive active materials such as manganese dioxide, cobalt hydroxide, polypyrrole were added to wood-derived carbon materials to increase their capacitance [22][23][24]. The latter is to enrich the electrode materials of double-layer capacitor, such as heteroatom doping, adjusting the surface shape and etching of carbon materials [25][26][27][28][29][30][31]. Many researchers have explored this method, such as B, O and N co-doped biomass derived graded porous carbon (382.5 F g -1 at 1 A g -l ) [60], the preparation of the B doped wood derived porous carbon (285.6 F g -1 at 1 A g -1 ) [49], and N doped biomass carbon (261 F g -1 at 0.5A g -1 ) [35] exhibited no special morphological characteristics, leading to a relatively low speci c surface area and thus a low contribution rate of the pseudocapacitance [32][33][34].…”