Li-decorated double vacancy graphene for hydrogen storage application: A first principles study S. Seenithurai, R. Kodi Pandyan, S. Vinodh Kumar, C. Saranya, M. Mahendran * Smart Materials Lab, Department of Physics, Thiagarajar College of Engineering, Madurai 625015, India article info Article history: Received 23 March 2014 Received in revised form 8 May 2014 Accepted 12 May 2014 Available online 11 June 2014 Keywords: Hydrogen storage Adsorption DFT Li-decoration Binding energy Defected graphene abstract Lithium decoration is an effective strategy for improving the hydrogen adsorption binding energy and the storage capacity in carbon nanostructures. Here, it is shown that Li- decorated double carbon vacancy graphene (DVG) can be used as an efficient hydrogen storage medium by means of Density Functional Theory (DFT) based calculations. The Li binding energy in DVG is 4.04 eV, which is much higher than that of pristine graphene. A maximum of four hydrogen molecules adsorb on Li decorated on one side of DVG and this leads to a gravimetric storage capacity of 3.89 wt% with an average adsorption binding energy of 0.23 eV/H 2 . When Li is decorated on both sides of DVG, the gravimetric storage capacity reaches 7.26 wt% with a binding energy of 0.26 eV/H 2 which shows that desorption would take place at ambient conditions. Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Introduction Hydrogen is one of the alternative energy resources with high abundance on the earth in the form of water. It is a clean energy carrier and produces water vapor as the only effluent during the combustion of the engine. It has high energy con- tent in terms of mass (~143.0 MJ/kg) which is three times larger than the gasoline (44.4 MJ/kg). However, in terms of volume, its efficiency is very low (0.0108 MJ/L), compared to gasoline (34.8 MJ/L) [1]. Thus, efficient storage and trans- portation are to be accomplished to use hydrogen as a fuel in fuel-cell controlled vehicles (FCV). A normal car would consume 4 kg of hydrogen to travel a distance of ~400 km. Since hydrogen is a molecular gas, in order to store 4 kg of hydrogen at normal temperature and pressure (NTP), a vol- ume of ~45 m 3 is required and this size would be larger than the car itself. Thus, storing hydrogen in a smaller, lightweight and safe container is one of the important problems that has to be addressed for onboard automobile applications [2,3]. Hydrogen is stored using physical method or chemical methods. Conventional physical hydrogen storage method is a high-pressure method where H 2 molecules are compressed to a high pressure in the aluminum cylinders or carbon fiber * Corresponding author. Tel.: þ91 452 2482430x723; fax: þ91 452 2483427. E-mail addresses: manickam-msahendran@tce.ed, perialangulam@gmail.com (M. Mahendran). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 39 (2014) 11016 e11026 http://dx.doi.org/10.1016/j.ijhydene.2014.05.068 0360-3199/Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.