Sum Frequency Generation Spectroscopy of Electrocatalyst Surfaces
Abstract
Catalytic reactions at solid liquid interfaces represent complex processes, which include local electrostatic fields within the double layer, hydrogen bonding, water solvation fields, orientational alignment of molecules, intermediate species and their associated barrier heights, and ultimately the overpotentials required to drive reactions and initiate charge transfer to the ions in solution. There are loss mechanisms associated with each of these key components within the overall electrocatalytic process. However, this complex process is often oversimplified in order to provide a basic interpretation of experimental data, largely because methods for separating these key components do not yet exist. The objective of this proposal is to apply surface selective spectroscopic tools to study and separate the key components of catalytic reactions at electrode surfaces, and to systematically vary precisely defined electrocatalytic structures in order to improve our understanding of energy flow and loss mechanisms in these systems. In the proposed work, we will measure the solvent structure, dynamics, molecular orientation, and reaction mechanisms at the surface of graphene based transparent electrodes in situ under electrochemical working conditions using sum frequency generation (SFG) spectroscopy. In particular, we will establish (1) How hydrogen bonding configurations of water molecules (number and geometric arrangement of donor and acceptor H bonds) are different near the interface vs. in bulk water, and how they are affected by the electrode potential, (2) How the molecular orientation of solvent and adsorbate molecules responds to electric fields at charged electrode surfaces, and (3) How the electrode potential and electrolyte concentration control the surface electrostatics, specifically the z dependence of the electric fields and spatial distributions of cation and anion concentrations.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 14, 2022
- Source ID
- FA95501910115
Entities
People
- Stephen B Cronin
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Southern California