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A review on modified carbon materials as promising agents for hydrogen storage

Posted on 28. August, 2018.

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Nowadays, energy is an important issue in all countries and this essential subject and the drawbacks of fossil fuels have encouraged researchers to develop new energies. However, among these new energies such as solar energy, wind energy and others, hydrogen is pre-eminent because it has no pollutant by-product and it is thus clean with a huge thermal energy. However, it is not applicable in many industries because of obstacles such as safety, volatility, explosive hazards and low compressibility. 

To resolve these problems, researchers have worked extensively on adsorbents such as metal-organic frameworks (MOFs), carbon structures and graphene compounds. Some authors have preferred to enhance pure adsorbents by adding additives such as free metals, alloys, metal oxides and others, and have studied different synthetic methods to clarify the effects of structure, diameter, porosity, morphology, and so on. For instance, many researchers concluded that the most important factor which impacts on adsorption is the specific surface area, and this parameter is highlighted in several papers. However, several articles have shown, by experimental and theoretical methods, that certain factors are able to overcome the influence of specific surface area on adsorption processes. For example, Zubizarreta et al. worked on the hydrogen adsorption on carbon structures at 77 and 273 K. From the specific surface area (SBET), the results reported in this work, namely CC-10, AC-P, AC-RA and AC-ER samples had different specific surface areas. Yet they had about the same hydrogen storage capacity. The authors attributed this apparent anomaly to the effect of pore volume. They divided pores into micropores and narrow micropores, and showed that carbon materials with large micropores had high hydrogen adsorption. Khoshnevisan et al. worked on the influence of diameter size on the adsorption process. The results obtained by theoretical methods showed a change in diameter size was able to act as an agent, to recognise the type of adsorbate–adsorbent bond (physisorption or chemisorption). Many researchers have worked on other adsorption parameters such as pore shape and interlayer distance. Zhu et al. worked on the effect of preparation methods: thus they synthesised g-C3N4 using three different reactants (urea, thiourea and melamine). The results showed that the resulting g-C3N4 samples had different adsorption capacities. The authors attributed these differences to the mechanism of synthesis and noted that the preparation of g-C3N4 using urea and thiourea caused the mechanism of adsorption processes to take place with additional subsidiary processes which produced H2O and NH3 as by-products. These materials escaped from the g-C3N4 surface at the transition state and induced additional porosity, and the TEM image confirmed this conclusion.

Read the full article in Science Progress.

DOI:https://doi.org/10.3184/003685018X15173975498956.


Authors: Siroos Rostami, Ali Nakhaei Pour and Mohammad Izadyar
Ferdowsi University of Mashhad, Iran
E-mails: siroosrostami90@gmail.com, a.nakhaei@um.ac.ir and zadyar@um.ac.ir

Keywords: carbon material, hydrogen, storage, gryphenne, nanotube, graphene, activated carbon

Image: Hydrogen spillover mechanism: step1, dissociation of molecular hydrogen and formation of TM-H bonds; step 2, migration of atomic hydrogen to the carbon surface; and step 3, diffusion of atomic hydrogen along the carbon surface. Reprinted with permission from Elsevier.