Theoretical Nonlinear Spectroscopic and Thermodynamic Study of Single Atom Catalyst Assisted Water Dissociation

• Applicant: Deepak Ojha, Ph.D.
• Subject Area: Theoretical Chemistry: Molecules, Materials, Surfaces ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Theoretical Chemistry: Electronic Structure, Dynamics, Simulation
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 550547050

Although, single-atom catalysts (SACs) stabilized on nitrogen-rich carbon materials have been extensively used for catalytic water-splitting, a thorough understanding of the overall reaction mechanism and thermodynamic profile of the reaction is still not achieved. This is particularly challenging when the multiple phases with several degrees of freedom involved in the overall reaction are treated within the ab- initio molecular dynamics (AIMD) framework. In this three-legged project, I propose to implement three computational methods directly applicable to enhance the understanding of SAC-driven water dissociation. In the first stage, we propose to develop and implement a time-correlation function-based formalism to obtain double-resonance sum-frequency generation (DR-SFG) that can unravel electronic-vibrational coupling between the SAC/substrate/water degrees of freedom and its role in water-dissociation. We will employ the linear-response time-dependent density functional theory (LR-TDDFT) and AIMD to sample the accessible electronic states and their corresponding transition dipole moment, polarisability, and excitation energy. In the second stage, we will use the short-window wavelet transform method to obtain time-dependent intermolecular (terahertz) frequencies of the water solvation shell around the SAC. This is particularly important as local solvent (water) molecules can lower the reaction barrier, and stabilize the intermediates or transition states. In the final stage, we will extend the 2 Phase Thermodynamics (2PT) formulation for water dissociation on the surfaces. This will let us estimate not only the free energy for water dissociation on the surface but also help us decipher the contribution of enthalpy and entropy to the reaction barrier. Finally, we will investigate the water dissociation using transition metals-based SACs (Pt, Pd, and Fe) and main group bases SACs (like sulfur) on the nitrogen-rich carbon materials (g-C3N4 and C2N). The role of defects in the substrate and external static electric field will also be explored.

• DFG Programme: Research Grants