Energetics and Dynamics of CO Oxidation and H₂O Dissociation on Pt(111) under Two-Dimensional Confinement

Tiwari, Nidhi (2025) Energetics and Dynamics of CO Oxidation and H₂O Dissociation on Pt(111) under Two-Dimensional Confinement. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Nidhi Tiwari (17IP015)) 17IP015.pdf - Submitted Version Restricted to Repository staff only Download (26MB)

Abstract

In recent years, nano-scale confinement has emerged as a promising strategy to enhance and modify catalytic processes, particularly within simpler confined spaces formed between two-dimensional (2D) materials and metal surfaces. CO oxidation and H₂O dissociation are critical steps in various catalytic processes and have been extensively investigated for their energetics and dynamics. However, the impact of confinement on the dynamics of these reactions has not been thoroughly explored, despite reports indicating a positive influence of 2D confinement on their activation barriers. To bridge this gap, posttransition-state dynamics of CO oxidation on Pt(111) under graphene (Gr) confinement was studied at different temperatures using ab initio molecular dynamics (AIMD) method based on density functional theory (DFT). Our results reveal a pronounced temperaturedependent effect of confinement, with the reactivity enhancement being more significant at lower temperatures. A comparative study of other 2D materials, specifically pristine and defected hexagonal boron nitride (h-BN) and heptazine-based graphitic carbon nitride (g-C₃N₄), showed that h-BN with a nitrogen single-vacancy (NV) is more effective than Gr in lowering the activation barrier. Dynamical simulations further emphasize the role of these overlayers in modulating product desorption dynamics, with NV and Gr inducing unique vibrational behaviors in the desorbing CO₂. The effects of Gr, pristine h-BN and g-C₃N₄ overlayers on the activation barrier, reaction path and vibrational frequencies pertaining toH2O dissociation on Pt(111) were evaluated, revealing their dependence on the overlayer properties. The influence of overlayer heights on the adsorption energy was assessed as well. Pristine h-BN and g-C₃N₄ exhibited considerable barrier reduction for H₂O dissociation compared to CO oxidation, indicating reaction-specific effects. Utilizing harmonic transition state theory with quantum tunneling corrections, reaction rate constants were computed to emphasize the tunable nature of catalytic behavior under confinement. This work will bring a deeper understanding of the mechanistic role of 2D confinement in catalytic processes, and lay down the foundations for designing advanced catalytic systems.

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