Hetero-atoms as activation centers for hydrogen absorption in carbon nanotubes

Abstract

Carbon materials should have specific centers for hydrogen adsorption/absorption. The role of heteroatom substitution in carbon nanotubes as an activator has been identified by Density Functional Theory. The effect of various hetero-atoms like nitrogen, phosphorus, sulphur and boron for hydrogen activation and their geometrical positions has been recognized as the one of the possible centre for easy hydrogenation. Experimentally nitrogen and boron containing carbon nanotubes have been synthesized using template method. The hydrogen absorption capacity of these materials has been evaluated. It is also shown that it is necessary to stabilize nitrogen in the carbon nanotube framework for reproducible hydrogen uptake. In case of boron containing carbon nanotubes having different chemical environments for boron shows a maximum of 2 wt% of hydrogen storage capacity at 80 bar and 300 K. This configuration has a bearing in hydrogen sorption characteristics.