An Overview of the Recent Progress in Modifications of Carbon Nanotubes for Hydrogen Adsorption

Abstract

Many researchers have carried out experimental research and theoretical analysis on hydrogen storage in carbon nanotubes (CNTs), but the results are very inconsistent. The present paper reviewed recent progress in improving the hydrogen storage properties of CNTs by various modifications and analyzed the hydrogen storage mechanism of CNTs. It is certain that the hydrogen storage in CNTs is the result of the combined action of physisorption and chemisorption. However, H2 adsorption on metal-functionalized CNTs still lacks a consistent theory. In the future, the research of CNTs for hydrogen adsorption should be developed in the following three directions: (1) A detailed study of the optimum number of metal atoms without aggregation on CNT should be performed, at the same time suitable preparation methods for realizing controllable doping site and doped configurations should be devised; (2) The material synthesis, purification, and activation methods have to be optimized; (3) Active sites, molecular configurations, effectively accessible surface area, pore size, surface topology, chemical composition of the surface, applied pressure and temperature, defects and dopant, which are some of the important factors that strongly affect the hydrogen adsorption in CNTs, should be better understood.

Hydrogen Nanometrology in Advanced Carbon Nanomaterial Electrodes

“…The electrochemical charge-discharge mechanism in SWCNT paper electrodes is known to be controlled by a proton diffusion process, and somewhere in between a physical process (as in pure carbon nanotubes) and a chemical process (as in metal hydride electrodes). It consists of a charge transfer reaction (reduction/oxidation) and a diffusion step (diffusion) [ 40 ].…”

Characterization of Carbon Materials for Hydrogen Storage and Compression

“…In addition to the aforementioned, abnormally high results, the hydrogen adsorption capacity of CNTs barely exceeds 1 wt.% at room temperature [67,78]. Indeed, the hydrogen uptake does not depend on the textural properties of CNTs as for temperatures close to 77 K. Thus, decorating CNTs with metal nanoparticles was found to be a good way of improving the hydrogen uptake due to the spillover phenomenon [79].…”

“…Indeed, the hydrogen uptake does not depend on the textural properties of CNTs as for temperatures close to 77 K. Thus, decorating CNTs with metal nanoparticles was found to be a good way of improving the hydrogen uptake due to the spillover phenomenon [79]. The most frequent doping with metal nanoparticles is based on Pd, Mg, Ni, Ti, Li, and Al [78] using different types of methods including impregnation, reduction in situ or sputtering [67]. In this sense, an essential requirement during the functionalization of CNTs is to prevent the obstruction of the available pores, which would decrease the surface area.…”

“…Figure 9a,b shows the hydrogen uptakes (in excess) at 77 and 298 K, respectively, obtained on CNFs, CNTs, and GOs reported in recent years. to metal nanoparticles for doping carbon materials can be with heteroatoms such as N, P, Si, and B [78]. Ariharan et al [84] synthesized N-doped CNTs from polymeric precursors, such as polystyrene and polypyrrole, by poly-condensation followed by carbonization under an inert atmosphere.…”

Recent advancement in consolidation of MOFs as absorbents for hydrogen storage

“…39 Carbon nanotubes (CNTs) and their composites have received significant research attention for their potential application in hydrogen storage technologies owing to their unique properties. 40,41 The research on CNTs as potential hydrogen storage material has been accelerated after Dillon et al 42 stated that single-walled carbon nanotubes (SWNT) could store hydrogen in the range of 5-10 wt% at ambient temperature. However, hydrogen stored on bare MWCNTs show weak interactions between the MWCNTs and H 2 which impact negatively on its ability to store hydrogen.…”