Be doped carbon nanoring for hydrogen storage using density functional theory

Abstract

We have studied hydrogen uptake properties of Be doped carbon nanoring structures using density functional theory. The nanoring considered consists of five six-membered carbon rings bonded through CC bond. Different doping sites are considered for Be doping. Four possible doping sites lead to four different structures named as CNR1, CNR2, CNR3, CNR4. Five, five, ten and five Be atoms are doped in CNR1, CNR2, CNR3, CNR4 respectively. All the Be doped carbon nanoring structures are thermodynamically stable as indicated by the formation energies and are more stable than undoped carbon nanoring structures as indicated by cohesive energy. The stability of all the four structures is also confirmed by performing ab initio molecular dynamics simulations and vibrational spectra. One, two, two and two H2 molecules get adsorbed per Be atom in CNR1, CNR2, CNR3, CNR4 structures respectively with respective hydrogen storage capacity of 2.42, 4.73, 9.04 and 4.73 wt%. H2 adsorption is thermodynamically favorable below 350, 175, 205 and 70 K on CNR1, CNR2, CNR3, CNR4 respectively with respective desorption temperature (desorption energy) of 652(0.72), 388(0.52), 438(0.55) and 148 K (0.33 eV). Position of doping site affects the number of hydrogen molecule adsorption per Be atom, H2 uptake capacity and other properties.