Hydrogen storage remains a key challenge for the advancement of hydrogen and fuel cell technologies in stationary and portable applications, and especially in transportation. In the past the majority of research effort has been devoted to the development of on-board vehicular hydrogen storage systems which will be cheap, light, safe, reversible, and will permit a driving range of ~500 km. The last 15 years of intensive research has shown that the material which can fulfil all these requirements does not exist yet. The main challenge and difficulty is to synthesize adsorbents showing an accessible specific surface for adsorption larger than 3500 m2/g and a binding energy of adsorption above 8 kJ/mol. These minimal criteria They are also the minimal goal of this project.

The HYSTOR project proposes a new approach of synthesis of a new class of porous, carbon-based hybrid materials which aim to be optimal adsorbents of hydrogen for mobile applications.
The project addresses both theoretical and experimental aspects of the problem of efficient H2 storage by physisorption. The proposed research protocol includes all aspects of development of new material for practical application:
  • the synthesis of new adsorbents,
  • their characterization,
  • multiscale numerical modeling.
1) The synthesis of the porous systems will use the arc discharge approach which has been used for over 20 years to produce fullerenes and carbon nanotubes. We will incorporate B and N atoms during the synthesis of the carbon scaffolds. This technique, already used for the synthesis and doping of carbon nanotubes, requires high temperatures, typically around 3000 K. It has already been proved that up to 33 % of N can be incorporated into such carbon structures using high temperature techniques (such as arc discharge but also laser ablation or magnetron sputtering). The advantage of this approach is the possibility to prepare significant quantities of material for in depth characterization. It will also be possible to upscale this approach in a future step. The main challenge of this project will be the optimization of existing procedure to obtain porous ensembles of graphene scaffolds (nano-fragments) with a high percentage of carbon atoms substituted by boron and /or nitrogen atoms.

2) A large variety of techniques will be used to fully characterize the synthesized structures. Samples morphology will be analyzed using transmission electron microscopy. Spatially resolved electron energy loss spectroscopy (EELS) will be carried-out to check for the actual N and/or B-by-C substitution and quantify the substitution rate. Nitrogen and argon physisorption will be used to determine the samples’ specific surface and pore size distribution. The energies of adsorption will be measured using calorimetric methods. The hydrogen adsorption measurements will be performed both at low temperature (30-80 K) and at room temperature and up to pressures of 200 bars. The final storage capacity of the materials will be estimated from hydrogen isotherms.

3) These experimental aspects will be supplemented by the multi-scale numerical modeling of the structural stability, binding energy of adsorption and the simulations of isotherms of hydrogen adsorption. The role of the numerical research will consist in guiding the experimental synthesis, proposing a microscopic mechanism of adsorption and complementing the material characterization by information that is not accessible from experimental data (for example, models of distribution of substituted atoms, distribution of the energy of adsorption and local density of the adsorbed hydrogen). This information will provide a feedback for optimization of the experimental procedures, especially for more effective search of the substitution procedure and synthesis.