Recent studies have shown that titanium decoration of carbon nanotubes remarkably increases the capacity of the latter for hydrogen storage from the gas phase [1]. In the present study, the behavior of a single carbon layer (SCL) modified with titanium is studied in presence of oxygen and water. The blocking of hydrogen adsorption sites by the adsorption of oxygen molecules is analyzed. Furthermore, the interaction of the substrate with water is considered. The present results are relevant for electrochemical hydrogen storage, since in the latter case the hydrogen stored comes from water electrolysis.
The SCL was considered as an infinite system by means of periodic boundary conditions in x and y directions. For oxygen and water adsorption, the minimum energy path was found by means of the nudged elastic band method and density functional theory (DFT) calculations employing the SIESTA computer code [2], which uses a localized basis set to represent the Kohn-Sham orbital. Exchange and correlation effects were described using the generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) functional [3]. The basis set used was a double-z one plus polarization quality.
References
[1] T. Yildirim, S. Ciraci, Phys. Rev. Lett. 94 175501 (2005).
[2] E. Artacho, J. Gale, A. García, J. Junquera, P. Ordejón, D. Sánchez Portal, S.M. Soler
[3] J. P. Perdew, K. Burke, M. Ernzerhof, Phys. Rev. Lett. 77 3865 (1996).
