Abstract
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.
Highlights
The European Commission’s Directive 2009/28/EC (renewable energy sources (RES) directive) has established that at least 20% of energy consumption must come from RES by 2020, and EU countries have agreed to a target of 27% by 2030 [1]. RES, such as solar or wind, will play a significant role in electric power generation
The pores were larger for higher KOH/DPC ratios, leading to the presence of a microporous structure on the walls separating the macropores, which is shown in the insets
We confirm that the formation of porous cavities in the material was produced by the KOH activation process [33,34,35]
Summary
The European Commission’s Directive 2009/28/EC (renewable energy sources (RES) directive) has established that at least 20% of energy consumption must come from RES by 2020, and EU countries have agreed to a target of 27% by 2030 [1]. RES, such as solar or wind, will play a significant role in electric power generation. The most prominent disadvantage of RES is their variability, which needs to be balanced for electric grid stability. Long-term and large-capacity electricity storage is required, as well as reserve production capacity. Current storage systems present low energy densities or limited storage potential. There are different paths for the conversion of energy produced from RES into gaseous or liquid fuels
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