Quantum Mechanical Studies of Water Splitting Reaction With (ZNO)3 Nanoclusters as Catalysts

Author

Duwage C. Perera, University of MaineFollow

Date of Award

Spring 5-5-2023

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor

Jayendran C. Rasaiah

Second Committee Member

Scott Collins

Third Committee Member

Robert Lad

Additional Committee Members

Thomas Schwartz

Christopher Mundy

Michael Kienzler

Abstract

With the current energy crisis, H₂ production through the water-splitting reaction has drawn attention recently. In this thesis, I studied the structural (geometry) and electronic properties (vertical detachment energy and electron affinity) of ZnO monomers and dimers using density functional theory. ZnO is a metal oxide with a 3.37 eV band gap and can be a commercially cheaper photocatalyst in hydrogen (H₂) production. The B3LYP/DGDZVP2 pair was selected after investigating different pairs of exchange functionals and basis sets to study the hydration, hydrolysis, and water-splitting reaction. The singlet-triplet energy gaps of small (ZnO)_n clusters (n=1-6) of different sizes were compared and the (ZnO)₃ cluster was selected as an optimal cluster size to study the water-splitting reaction. A detailed study of water-splitting reaction pathways in the gas phase showed that oxygen is produced after hydrogen and the rate-determining step is the formation of the Zn-H bond. Graphene and graphene oxide (GO) based metal oxides play an important role as substrates for the photocatalytic reaction. The π conjugation structure of GO shows greater electron mobility and may enhance the photocatalytic performance of ZnO by increasing the electron-hole separation. In this work, I studied the impact of graphene and GO on (ZnO)3 in hydration and hydrolysis reaction using 2 water molecules and in producing H₂ and O₂ as products of water splitting reaction in the gas phase. I used 5 different GO models anchoring carboxyl, hydroxyl, and epoxy functional groups on a graphene layer to study the hydration and hydrolysis reaction with two water molecules. The (ZnO)₃ anchored on GO model 1 was used to study the water-splitting reaction pathway.

Recommended Citation

Perera, Duwage C., "Quantum Mechanical Studies of Water Splitting Reaction With (ZNO)3 Nanoclusters as Catalysts" (2023). Electronic Theses and Dissertations. 3749.
https://digitalcommons.library.umaine.edu/etd/3749