Role of defects and dopants in zinc oxide nanotubes for gas sensing and energy storage applications

• Published in: International journal of energy research Vol. 44; no. 13; pp. 10926 - 10936
• Main Authors: Ali, Muhammad, Tit, Nacir, Yamani, Zain H.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Inc 25.10.2020; Hindawi Limited
• Subjects: Adsorption; Charge transfer; Chemisorption; Defects; Density functional theory; Dopants; Electrical conductivity; Electrical resistivity; Energy; Energy charge; Energy gap; Energy storage; gas sensing; Gas sensors; H2 molecules; Hydrogen storage materials; Nanotechnology; Nanotubes; Palladium; physisorption; Platinum; Splitting; Zinc; Zinc oxide; Zinc oxides; ZnO nanotube
• ISSN: 0363-907X; 1099-114X
• DOI: 10.1002/er.5656

Summary Spin‐polarized density functional theory (DFT) is employed to study the adsorption of H2 gas molecules on zinc oxide nanotubes (ZnO‐NTs) with intrinsic defects (oxygen and zinc vacancies) and dopants (Pd and Pt). Results indicate that defects lead to a strong chemisorption process, associated with strong splitting of the H2 molecule, rendering an irreversible process; that is, desorption is not possible. Such strong chemisorption process results in large adsorption energy and charge transfer between the defective‐ZnO‐NTs and H2 molecules. On the other hand, a weaker chemisorption process, associated with weak splitting of H2 molecule, takes place in the case of Pd or Pt dopants. The chemisorption of H2 on defective sites and dopants changes the energy gap to a large extent, resulting in major changes in the electrical conductivity of the ZnO‐NTs and consequently revealing their relevance for gas sensing applications with an enhancement of sensor response. From a different perspective, Pd ought to be a good dopant for ZnO‐NT based hydrogen storage material as it weakens the adsorption strength between H2 and ZnO‐NT. Defects (VOand VZn) cause strong splitting of H2 molecule and enhances sensor response in gas sensing applications; whereas dopants (Pd and Pt) cause weak splitting of H2 molecule and would be more useful in energystorage applications.