In this study, we present willow wood as a new low-cost, renewable, and sustainable biomass source for the production of a highly porous activated carbon for application in energy storage devices. The obtained activated carbon showed favorable features required for excellent electrochemical performance such as high surface area (∼2 800 m² g^–1) and pore volume (1.45 cm³ g^–1), with coexistence of micropores and mesopores. This carbon material was tested as an electrode for supercapacitor application and showed a high specific capacitance of 394 F g^–1 at a current density of 1 A g^–1 and good cycling stability, retaining ∼94% capacitance after 5 000 cycles (at a current density of 5 A g^–1) in 6 M KOH electrolyte. The prepared carbon material also showed an excellent rate performance in a symmetrical two-electrode full cell configuration using 1 M Na₂SO₄ electrolyte, in a high working voltage of 1.8 V. The maximum energy density and power density of the fabricated symmetric cell reach 23 W h kg^–1 and 10 000 W kg^–1, respectively. These results demonstrate that willow wood can serve as a low-cost carbon feedstock for production of high-performance electrode material for supercapacitors.

The excellent functional properties of graphene and micro-nanofibrillated cellulose (MNFC) offer plenty of possibilities for wide ranging applications in combination as a composite material. In this study, flexible graphene/microfibrillated cellulose (MFC) composite films were prepared by a simple method of co-exfoliation of graphite in an MFC suspension by high-shear exfoliation. We show that pristine graphene, without any chemical treatment, was homogeneously dispersed in the MFC matrix, and the produced composites showed enhanced thermal, electrical and mechanical properties compared to a non-co-exfoliated control. The film properties were studied by XPS, XRD, Raman, SEM, FTIR, TGA, nitrogen sorption, UV-vis spectroscopy, optical and formation analysis tests. At 0.5 wt% loading, the specific surface area of graphene/MFC composites increased from 218 to 273 m² g⁻¹ while the tensile strength and Young's modulus for the graphene/MFC composites increased by 33% and 28% respectively. Thermal stability was enhanced by 22% at 9 wt% loading and the composites showed a high electrical conductivity of 2.4 S m⁻¹. This simple method for the fabrication of graphene/MFC composites with enhanced controlled functional properties can prove to be industrially beneficial, and is expected to open up a new route for novel potential applications of materials based largely on renewable resources.