Pine sawdust-derived cellulose nanocrystal/polypyrrole composites with enhanced electrochemical performance for...

In this study, cellulose nanocrystals (CNC) were successfully extracted from pine sawdust through alkali pretreatment, oxidative bleaching with an H₂O₂/CH₃COOH system, and subsequent sulfuric acid hydrolysis. Structural characterization by FT-IR, XRD, and FE-SEM confirmed the preservation of the cellulose I crystalline structure and the formation of rod-like CNC with nanoscale dimensions. A conductive polypyrrole/cellulose nanocrystal (PPy/CNC) composite was synthesized via in situ chemical polymerization of pyrrole in the presence of CNC, with an optimal Py : CNC mass ratio of 1 : 1 yielding a homogeneous and well-dispersed composite. UV-Vis, FT-IR, and XRD analyses revealed strong interfacial interactions between PPy and CNC, whereas BET analysis confirmed an increased specific surface area and the formation of a hierarchical mesoporous architecture. The CNC framework effectively suppressed PPy aggregation, facilitated electrolyte-ion transport, and promoted the formation of interconnected conductive pathways. Electrochemical measurements demonstrated that the PPy/CNC electrode exhibited pronounced pseudocapacitive behavior, delivering a specific capacitance of 287.4 F g^-1 at 2 mV s^-1 and 137.1 F g^-1 at 20 mV s^-1 in 1 M KCl electrolyte. The assembled symmetric supercapacitor achieved an energy density of 6.26 Wh kg^-1 at a power density of 443.41 W kg^-1 (1 A g^-1), while retaining 74.1% of its initial capacitance after 3000 charge-discharge cycles. These findings demonstrate the synergistic role of biomass-derived CNC in improving electrode architecture, facilitating ion transport, and enhancing electrochemical performance, highlighting the potential of sustainable PPy/CNC composites as promising electrode materials for high-performance supercapacitors.