A sustainable bio-based char as emerging electrode material for energy storage applications.

In the last few years, extensive research efforts have been made to develop novel bio-char-based electrodes using different strategies starting from a variety of biomass precursors as well as applying different thermochemical conversion paths. In this regard, hydrothermal carbonization method is becoming a more prevalent option among conversion procedures even if pyrolysis remains crucial in converting biomass into carbonaceous materials. The main aim of this study is to develop an innovative supercapacitor electrode from spruce bark waste through a unique low-temperature technique approach, which proved to effectively eliminate the pyrolysis step. Consequently, a hybrid spruce-bark-graphene oxide compound (HySB) was obtained as electrode material for supercapacitors. When compared to a regularly used commercial electrode material, SLC1512P graphite (reference) with 150.3 µF cm-2 capacitance, the HySB has a substantially higher capacitive performance of 530.5 µF cm-2. In contrast to the reference, the HySB polarization resistance increases by two orders of magnitude at the stationary potential and by three orders of magnitude at the optimum potential, underlying that the superior performances of HySB extend beyond static conditions. The synthesis strategy provides an appropriate energy-efficient option for converting biomass into carbonaceous materials with meaningful properties suitable for energy storage applications.

Hydrothermal Carbon as Reactive Fillers to Produce Sustainable Biocomposites with Aromatic Bio-Based Epoxy Resins.

Thiswork is focused on the development of sustainable biocomposites based on epoxy bioresin reinforced with a natural porous material (hydrochar, HC) that is the product of spruce bark wastes subjected to hydrothermal decomposition. To identify the influence of hydrochar as a reinforcing material on the designed composites, seven formulations were prepared and tested. An aromatic epoxy monomer derived from wood biomass was used to generate the polymeric matrix, and the formulations were prepared varying the filler concentration from 0 to 30 wt %. The reactivity of these formulations, together with the structural, thermal, and mechanical properties of bio-based resin and biocomposites, are investigated. Surprisingly, the reactivity study performed by differential scanning calorimetry (DSC) revealed that HC has a strong impact on polymerization, leading to an important increase in reaction enthalpy and to a decrease of temperature range. The Fourier Transform Infrared Spectroscopy (FT-IR) investigations confirmed the chemical bonding between the resin and the HC, while the dynamic mechanical analysis (DMA) showed increased values of crosslink density and of storage moduli in the biocomposites products compared to the neat bioresin. Thermogravimetric analysis (TGA) points out that the addition of hydrochar led to an improvement of the thermal stability of the biocomposites compared with the neat resorcinol diglycidyl ether (RDGE)-based resin (T5% = 337 °C) by ≈2-7 °C. Significantly, the biocomposites with 15-20 wt % hydrochar showed a higher stiffness value compared to neat epoxy resin, 92SD vs. 82SD, respectively.