Hydrogen Adsorption and Associated Electronic and Magnetic Properties of Rh-Decorated (8,0) Carbon Nanotubes Using Density Functional Theory

Abstract

A systematic spin-polarized density functional theory (DFT) study of hydrogen interaction with pristine and Rh-decorated zigzag (8,0) single-walled carbon nanotubes (SWCNTs) was performed. The most stable decoration site for Rh atoms as well as atomic and molecular hydrogen adsorption inside and outside the SWCNT was studied. Hydrogen adsorption energy in Rh-decorated SWCNTs was improved compared to that of pristine nanotubes. In addition, Rh-decorated SWCNT systems present a magnetic moment. Density of states and work function (WF) were computed to study the bonding evolution and electronic structure. When hydrogen is considered on Rh-SWCNT and pristine SWCNT, the WF increased while band gap decreased compared to that of pristine SWCNT.

Rhodium clustering process on defective (8,0) SWCNT: Analysis of chemical and physical properties using density functional theory

“…The The binding energy (Eb), magnetic moment (µ), and work function (WF) obtained for each case are presented in Table 5. In a previous work where the Rh single atom adsorption on the pristine (8,0) SWCNT was studied, we found that the binding energy value is 2.67 eV [30]. It can be noted that the oxygenated and non-oxygenated vacancy incorporation improves the adsorption of one Rh atom (7.56 eV and 5.12 eV respectively).…”

“…The perpendicular vacancy configuration does not have a magnetic moment and its electronic structure behaves like a semiconductor with a band gap of 0.48 eV. In a previous work we have found that the pristine (8,0) SWCNT is a semiconductor with a relatively large band gap (Eg = 0.58 eV) and without magnetic moment [30]. Moreover, the Fermi level of pristine (8,0) SWCNT is located near to the valence band (VB); then its behavior resembles a p-type semiconductor.…”

“…The work function is computed as the difference between vacuum and Fermi levels. The WF for a pristine SWCNT is 4.39 eV [30]. The presence of a vacancy increases the WF about 11% (7%) for perpendicular (parallel) configuration.…”

“…The other C atoms -that form the defect-lose charge 0.01 eto 0.05 e -. The remaining atoms practically do not change their charge compared to the pristine nanotube [30]. The adsorption of O2 molecules in the SWCNT with vacancy will be discussed in detail in the following section.…”

“…On the other hand, it is well known that the addition of TM to a CNT improves hydrogen adsorption as well as electrical contact [25][26][27][28][29]. The TMs that have been investigated most widely as possible candidates are Rh, Ti, Pd, Al, and Pt [24,[30][31][32][33]. Recently, it has been reported that Rhodium shows a quite different surface behavior on SWCNTs compared to Ti interacting less strongly with oxygen [24,33].…”