(574c) Ab Initio Study of Single Pd Atom Functionalized Single-Walled Carbon Nanotubes as Novel Hydrogen Sensing Materials

Pd functionalized single-walled carbon nanotubes (SWNTs) have recently been used in gas sensing applications.[1,2] Functionalized CNTs have shown significant advantages as sensor materials, and can detect many types of molecules which are not sensitive to the pristine carbon nanotubes. In this paper, we study the electronic properties of Pd atom modified SWNTs and their interactions with hydrogen molecules. The calculations were performed using pseudo-potential plane wave method within the Density Functional Theory (DFT) and the Generalized Gradient Approximation of Perdew and Wang, known as PW91. Two types of SWNTs, armchair tube and zigzag tube, were studied. The interaction between Pd atom and SWNTs leads to a chemisorption bonding involving charge transfer. The electronic structures around Fermi level for both types of tubes were significantly modified. A transformation of zigzag tube from semiconductor to metal was observed. When loaded with hydrogen, more charge transferred from SWNTs to PdH complex, as a result, the SWNT gained more holes as carriers for increased conductance. The current-voltage characteristics will be compared with experimentally measured hydrogen sensors. The sensing mechanism for hydrogen detection using Pd-SWNT as sensing material will be investigated in detail. Calculations of binding energies, charge transfer, density of states and band gap will be presented with the performance of different type tubes explored in detail.

References

[1]. J. Kong, M. G. Chapline, and H. Dai, Adv. Mater. 13, 1384 (2001).

[2]. Y. Lu, et al. Chem. Phys. Lett. 391, 344 (2004).