Effects of defects on nanoporous Graphene and MOS2
- Oviroh, Peter Ozaveshe, Mohlala, Lesego M., Jen, Tien-Chien
- Authors: Oviroh, Peter Ozaveshe , Mohlala, Lesego M. , Jen, Tien-Chien
- Date: 2020
- Subjects: Defects , Graphene , Molecular Dynamics
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/464543 , uj:41505 , Citation:
- Description: Abstract: Please refer to full text to view abstract.
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- Authors: Oviroh, Peter Ozaveshe , Mohlala, Lesego M. , Jen, Tien-Chien
- Date: 2020
- Subjects: Defects , Graphene , Molecular Dynamics
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/464543 , uj:41505 , Citation:
- Description: Abstract: Please refer to full text to view abstract.
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Influence of single and double-atom metal doping on the electrocatalytic hydrogen evolution activity of 2D-MoS2 surface
- Mohlala, Lesego M., Oviroh, Peter O., Jen, Tien-Chien, Olubambi, Peter A.
- Authors: Mohlala, Lesego M. , Oviroh, Peter O. , Jen, Tien-Chien , Olubambi, Peter A.
- Date: 2020
- Subjects: Atomic doping , Density functional theory , Hydrogen evolution reaction
- Language: English
- Type: Conference Proceedings
- Identifier: http://hdl.handle.net/10210/461510 , uj:41110 , Citation: Mohlala, L.M. et al. 2020. Influence of single and double-atom metal doping on the electrocatalytic hydrogen evolution activity of 2D-MoS2 surface.
- Description: Abstract: The Hydrogen evolution reaction (HER) is an important process during electrocatalytic water splitting for hydrogen energy generation. Two dimensional (2D) MoS2 has been considered as a promising alternative to Pt-based catalysts in the hydrogen evolution reaction. However, the highest contribution for the catalytic activity of 2D-MoS2 is from its edge sites, this in turn leaves many in-plane domains useless. In this study, the effect of single atom metal (Pt, Ni and Pt-Ni) doping on HER catalytic activity of in-plane atoms was investigated using density functional theory calculations. The Gibbs free energy of adsorbed hydrogen on pristine MoS2 decreased from 1.86eV to -0.08eV in PtNi co-doped MoS2. This demonstrates enhanced catalytic activity of MoS2 due to atomic doping. The enhanced catalytic activity may also be attributed to the observed changes and increase in the density of electronic states near the Fermi energy level.
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- Authors: Mohlala, Lesego M. , Oviroh, Peter O. , Jen, Tien-Chien , Olubambi, Peter A.
- Date: 2020
- Subjects: Atomic doping , Density functional theory , Hydrogen evolution reaction
- Language: English
- Type: Conference Proceedings
- Identifier: http://hdl.handle.net/10210/461510 , uj:41110 , Citation: Mohlala, L.M. et al. 2020. Influence of single and double-atom metal doping on the electrocatalytic hydrogen evolution activity of 2D-MoS2 surface.
- Description: Abstract: The Hydrogen evolution reaction (HER) is an important process during electrocatalytic water splitting for hydrogen energy generation. Two dimensional (2D) MoS2 has been considered as a promising alternative to Pt-based catalysts in the hydrogen evolution reaction. However, the highest contribution for the catalytic activity of 2D-MoS2 is from its edge sites, this in turn leaves many in-plane domains useless. In this study, the effect of single atom metal (Pt, Ni and Pt-Ni) doping on HER catalytic activity of in-plane atoms was investigated using density functional theory calculations. The Gibbs free energy of adsorbed hydrogen on pristine MoS2 decreased from 1.86eV to -0.08eV in PtNi co-doped MoS2. This demonstrates enhanced catalytic activity of MoS2 due to atomic doping. The enhanced catalytic activity may also be attributed to the observed changes and increase in the density of electronic states near the Fermi energy level.
- Full Text:
Initial reaction mechanism on the atomic layer deposition of platinum on a graphene surface : a density functional theory study
- Mohlala, Lesego M., Jen, Tien-Chien, Olubambi, Peter A.
- Authors: Mohlala, Lesego M. , Jen, Tien-Chien , Olubambi, Peter A.
- Date: 2019
- Subjects: ALD , DFT , Finite temperature
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/400059 , uj:33371 , Citation: Mohlala, L.M., Jen, T.C. & Olubambi, P.A. 2019. Initial reaction mechanism on the atomic layer deposition of platinum on a graphene surface : a density functional theory study.
- Description: Abstract: The atomic layer deposition (ALD) of platinum on carbon supports has been studied extensively due to the wide potential application in microelectronics and catalysis. The initial reaction mechanism of atomic layer deposited platinum on a hydroxylated graphene surface has been investigated using density functional theory (DFT). Methylcyclopentadienyl trimethylplatinum (MeCpPtMe3) and molecular oxygen were adopted as precursors. In addition, finite temperature calculations were performed to investigate the effect of process conditions. The free energies were calculated at temperatures 200°C and 300°C with pressure of 1Pa. The results obtained from the simulations were compared and correlated with available literature.
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- Authors: Mohlala, Lesego M. , Jen, Tien-Chien , Olubambi, Peter A.
- Date: 2019
- Subjects: ALD , DFT , Finite temperature
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/400059 , uj:33371 , Citation: Mohlala, L.M., Jen, T.C. & Olubambi, P.A. 2019. Initial reaction mechanism on the atomic layer deposition of platinum on a graphene surface : a density functional theory study.
- Description: Abstract: The atomic layer deposition (ALD) of platinum on carbon supports has been studied extensively due to the wide potential application in microelectronics and catalysis. The initial reaction mechanism of atomic layer deposited platinum on a hydroxylated graphene surface has been investigated using density functional theory (DFT). Methylcyclopentadienyl trimethylplatinum (MeCpPtMe3) and molecular oxygen were adopted as precursors. In addition, finite temperature calculations were performed to investigate the effect of process conditions. The free energies were calculated at temperatures 200°C and 300°C with pressure of 1Pa. The results obtained from the simulations were compared and correlated with available literature.
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Nanoporous MoS2 membrane for water desalination : a molecular dynamics study
- Oviroh, Peter Ozaveshe, Jen, Tien-Chien, Ren, Jianwei, Mohlala, Lesego M., Warmbier, Robert, Karimzadeh, Sina
- Authors: Oviroh, Peter Ozaveshe , Jen, Tien-Chien , Ren, Jianwei , Mohlala, Lesego M. , Warmbier, Robert , Karimzadeh, Sina
- Date: 2021
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/482036 , uj:43697 , Citation: Oviroh, P.O. et al. 2021. Nanoporous MoS2 membrane for water desalination : a molecular dynamics study.
- Description: Abstract: Molybdenum disulfide (MoS2), a two-dimensional (2D) material, promises better desalination efficiency, benefiting from the small diffusion length. While the monolayer nanoporous MoS2 membrane has great potential in the reverse osmosis (RO) desalination membrane, multilayer MoS2 membranes are more feasible to synthesize and economical than the monolayer MoS2 membrane. Building on the monolayer MoS2 membrane knowledge, the effects of the multilayer MoS2 membrane in water desalination were explored, and the results showed that increasing the pore size from 3 to 6 Å resulted in higher permeability but with lower salt rejection. The salt rejection increases from 85% in a monolayer MoS2 membrane to about 98% in a trilayer MoS2 membrane. When averaged over all three types of membranes studied, the ions rejection follows the trend of trilayer > bilayer > monolayer. Besides, a narrow layer separation was found to play an important role in the successful rejection of salt ions in bilayer and trilayer membranes. This study aims to provide a collective understanding of this high permiselective MoS2 membrane’s realization for water desalination, and the findings showed that the water permeability of the MoS2 monolayer membrane was in the order of magnitude greater than that of the conventional RO membrane and the nanoporous MoS2 membrane can have an important place in the purification of water.
- Full Text:
- Authors: Oviroh, Peter Ozaveshe , Jen, Tien-Chien , Ren, Jianwei , Mohlala, Lesego M. , Warmbier, Robert , Karimzadeh, Sina
- Date: 2021
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/482036 , uj:43697 , Citation: Oviroh, P.O. et al. 2021. Nanoporous MoS2 membrane for water desalination : a molecular dynamics study.
- Description: Abstract: Molybdenum disulfide (MoS2), a two-dimensional (2D) material, promises better desalination efficiency, benefiting from the small diffusion length. While the monolayer nanoporous MoS2 membrane has great potential in the reverse osmosis (RO) desalination membrane, multilayer MoS2 membranes are more feasible to synthesize and economical than the monolayer MoS2 membrane. Building on the monolayer MoS2 membrane knowledge, the effects of the multilayer MoS2 membrane in water desalination were explored, and the results showed that increasing the pore size from 3 to 6 Å resulted in higher permeability but with lower salt rejection. The salt rejection increases from 85% in a monolayer MoS2 membrane to about 98% in a trilayer MoS2 membrane. When averaged over all three types of membranes studied, the ions rejection follows the trend of trilayer > bilayer > monolayer. Besides, a narrow layer separation was found to play an important role in the successful rejection of salt ions in bilayer and trilayer membranes. This study aims to provide a collective understanding of this high permiselective MoS2 membrane’s realization for water desalination, and the findings showed that the water permeability of the MoS2 monolayer membrane was in the order of magnitude greater than that of the conventional RO membrane and the nanoporous MoS2 membrane can have an important place in the purification of water.
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Thermal stability and reactivity of titanium halide precursors for the atomic layer deposition of TiO2 on a Pt (111) surface
- Mohlala, Lesego M., Jen, Tien-Chien, Olubambi, Peter Apata
- Authors: Mohlala, Lesego M. , Jen, Tien-Chien , Olubambi, Peter Apata
- Date: 2020
- Subjects: ALD , DFT , Platinum
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/458243 , uj:40694 , Mohlala, L.M., Jen, T., Olubambi, P.A.: Thermal stability and reactivity of titanium halide precursors for the atomic layer deposition of TiO2 on a Pt (111) surface.
- Description: Abstract: Please refer to full text to view abstract.
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- Authors: Mohlala, Lesego M. , Jen, Tien-Chien , Olubambi, Peter Apata
- Date: 2020
- Subjects: ALD , DFT , Platinum
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/458243 , uj:40694 , Mohlala, L.M., Jen, T., Olubambi, P.A.: Thermal stability and reactivity of titanium halide precursors for the atomic layer deposition of TiO2 on a Pt (111) surface.
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