Pinecones, a common biomass waste, has an interesting composition in terms of cellulose and lignine content that makes them excellent precursors in various activated carbon production processes. The synthesized, nanostructured, activated carbon materials show textural properties, a high specific surface area, and a large volume of micropores, which are all features that make them suitable for various applications ranging from the purification of water to energy storage. Amongst them, a very interesting application is hydrogen storage. For this purpose, activated carbon from pinecones were prepared using chemical activation with different KOH/precursor ratios, and their hydrogen adsorption capacity was evaluated at liquid nitrogen temperatures (77 K) at pressures of up to 80 bar using a Sievert’s type volumetric apparatus. Regarding the comprehensive characterization of the samples’ textural properties, the measurement of the surface area was carried out using the Brunauer–Emmett–Teller method, the chemical composition was investigated using wavelength-dispersive spectrometry, and the topography and long-range order was estimated using scanning electron microscopy and X-ray diffraction, respectively. The hydrogen adsorption properties of the activated carbon samples were measured and then fitted using the Langmuir/ Töth isotherm model to estimate the adsorption capacity at higher pressures. The results showed that chemical activation induced the formation of an optimal pore size distribution for hydrogen adsorption centered at about 0.5 nm and the proportion of micropore volume was higher than 50%, which resulted in an adsorption capacity of 5.5 wt% at 77 K and 80 bar; this was an increase of as much as 150% relative to the one predicted by the Chahine rule.

Self-standing and flexible paper-like electrodes consisting of nano-sized Co₃O₄ nanoparticles encapsulated in nitrogen-doped graphite-like carbon fibers are synthesized by electrospinning followed by thermal treatment. Several studies have recently reported that encapsulating nano-sized metal oxides that display conversion reaction, such as manganese, iron and cobalt oxides, within the three-dimensional network of electrospun carbon fibers allows to remarkably improve the performances of lithium-ion batteries. In the present work, we challenge these reports with a study based on the optimization of the preparation and post-synthesis treatment parameters, and a very precise characterization of the structural, morphological and chemical properties of the composite materials leading to clear structure-electrochemical properties correlations. In particular, it is found that the electrochemical properties of a physical mixture of cobalt oxide nanoparticles and electrospun carbon nanofibers are equivalent to the ones of the electrospun nanocomposites, proving that the benefit of electrospun metal oxide-carbon nanocomposites is limited and that the “enhanced properties” claimed in the literature arise from imprudent comparisons.