Characterization of Carbon Materials for Hydrogen Storage and Compression

Abstract

<jats:p>Carbon materials have proven to be a suitable choice for hydrogen storage and, recently, for hydrogen compression. Their developed textural properties, such as large surface area and high microporosity, are essential features for hydrogen adsorption. In this work, we first review recent advances in the physisorption characterization of nanoporous carbon materials. Among them, approaches based on the density functional theory are considered now standard methods for obtaining a reliable assessment of the pore size distribution (PSD) over the whole range from narrow micropores to mesopores. Both a high surface area and ultramicropores (pore width &lt; 0.7 nm) are needed to achieve significant hydrogen adsorption at pressures below 1 MPa and 77 K. However, due to the wide PSD typical of activated carbons, it follows from an extensive literature review that pressures above 3 MP are needed to reach maximum excess uptakes in the range of ca. 7 wt.%. Finally, we present the adsorption–desorption compression technology, allowing hydrogen to be compressed at 70 MPa by cooling/heating cycles between 77 and 298 K, and being an alternative to mechanical compressors. The cyclic, thermally driven hydrogen compression might open a new scenario within the vast field of hydrogen applications.</jats:p>

Contemporary Approach to the Porosity of Dental Materials and Methods of Its Measurement

“…Additionally, the shape of the hysteresis loop, formed by the adsorption and desorption branch, allows qualitative interpretation of the pore shapes [98]. The calculation of the total pore volume and the mean pore diameter can be determined from the amount of vapour adsorbed at a relative pressure close to unity, by assuming that the pores are filled with the adsorbate in the bulk liquid state [100,101]. In the case of pore-size distribution, measured by the N 2 adsorption method, the Barrett-Joyner-Halenda (BJH) theoretical model, with the assumption of cylindrical pores, is the most commonly used [102,103], while advanced DFT and grand canonical Monte Carlo (GCMC) models have been developed for calculating the pore-size distribution from the CO 2 adsorption isotherm [104][105][106].…”

“…Nitrogen (at 77 K) is the most commonly used adsorptive to characterize the surface area of mesopores of 2-50 nm and macropores below 100 nm in diameter [102]. However, a small quadrupole moment of nitrogen molecule can give specific, adverse interaction in small micropores, various surface functional groups and exposed ions; therefore, some researchers recommend the use of Ar at 87 K [101,107]. In turn, the CO 2 method is frequently used to measure the structure of micropores and narrow constrictions with widths smaller than 2 nm, due to the greater kinetic energy of the molecules and speeding diffusion into the narrow pores [104,108,109].…”

Nanoporous Carbon Materials toward Phenolic Compounds Adsorption

“…• Micropores: pores that have a diameter < 2 nm, they are divided into pores their width less than 0.7 called ultramicropores or narrow micropores and pores in a range of 0.7 and 2 nm called supermicropores or micropores [4,28].…”

“…for textbooks and reviews see: Sanghi, Canevesi, Celzard, Thommes [40], and Fierro. 2020 [4]; Thommes 2015 [46]; Thommes 2014 [40]) [40]. Physisorption is a general phenomenon and occurs whenever an adsorbable gas (the adsorptive) is brought into contact with the surface of a solid (the adsorbent).…”

“…Phenolic compounds are present in the effluents of various industries such as oil refining, petrochemicals, pharmaceuticals, coking operations, resin manufacturing, plastics, paint, pulp, paper, and wood products. Discharge of these compounds without treatment may lead to serious health risks to humans, animals, and aquatic systems [4]. The presence of these compounds is attributed to a breakdown of natural organic materials in the water, flows water away from farmland, and discharge of wastes resulting from industries and humans uses in water resources.…”