Nanocomposites and nanomaterials

A DFT study for adsorption of CO and H2 on 
Pt-doped ZnO nanoclucter
Dzikovskyi V.Ye.1, Bovgyra O.V.1, Kovalenko M.V.1, Bovhyra R.V.2
1 Faculty of Physics, Ivan Franko National University of Lviv, 8a, Kyrylo and Mefodiy str., 79005 Lviv, Ukraine. 
E-mail: mariya.kovalenko@lnu.edu.ua
2 Pidstryhach Institute for Applied Problems of Mechanics and Mathematics NAS Ukraine, 3-b, Naukova str., 79060 Lviv, Ukraine.

Zinc oxide (ZnO) is a wurtzite semiconductor with band gap energy of 3.37 eV and it has very large excitation binding energy (60 meV) at room temperature. Nanostructured ZnO with different morphologies has been extensively studied for gas sensor applications due to its favorable morphological, microstructural and electrical properties. Doping is an important and effective method for improving the sensing properties of metal oxide semiconductors. The dopants change the gas sensing properties by changing the electronic properties and morphology, creating more centers for gas interaction on the metal oxide semiconductor surface.
In this work, the first-principles calculations method has been used to study the interactions between H2 and CO gas molecules and the Pt doped ZnO nanoclusters in order to suggest novel sensor to H2 and CO gas molecules detection. 
Full optimizations of pure and doped structures of (ZnO)12 nanocluster were carried out using density functional theory (DFT) method. Ultrasoft pseudopotentials were used to describe the interactions between the atomic nucleus and valence electrons, and the generalized gradient approximation (GGA) was used to describe the exchange-correlation energy of electrons. To more accurately describe the exchange and correlation potential, this study adopted the DFT+Ud+Up calculation method.
The adsorption of CO and H2 onto the Pt-doped ZnO nanoclusters is predicted to be different from that of a pristine nanocluster. The electronic properties of the Pt-doped ZnO cluster are sensitive toward the number of adsorbed CO molecules. In case adsorption H2 molecule, the first hydrogen molecule can be chemically adsorbed on the Pt atom without crossing any energy barrier, while the second hydrogen molecule can be chemically adsorbed on the Pt atom by crossing a small energy barrier. Up to two hydrogen molecules can be chemically adsorbed on a single Pt atom supported by the ZnO nanoclusters.