17. Prof. Sharon Hammes-Schiffer - Electrochemical Proton-Coupled Electron Transfer (Mar 17, 2022)

Full title: Theoretical Modeling of Electrochemical Proton-Coupled Electron Transfer
Speaker: Prof. Sharon Hammes-Schiffer (Department of Chemistry, Yale University, USA)

First Part:
00:00 - Everyone is getting connected
00:41 - Introduction
02:30 - Beginning of the talk
03:56 - Different types of PCET
06:05 - Single electron transfer
08:02 - Four- and two-state models for PCET
12:09 - Electron-proton vibronic states
17:49 - PCET theory: adiabatic and nonadiabatic mechanisms
28:50 - Kinetic isotope effect
30:21 - Proton donor-acceptor motion
32:26 - Related theories
34:10 - Homogeneous Electrochemical PCET
48:48 - Application of homogeneous PCET theory

First Q&A
1:04:24 - Q1: Orientation of the molecule during PCET
1:07:29 - Q2: IR detection of excited states
1:09:43 - Q3: Applicability to battery electrodes
1:10:56 - Q4: Dielectric image effect
1:13:34 - Q5: Collective solvent coordinate
1:17:31 - Q6: PCET Rate constant
1:19:24 - Q7: Landau-Zener theory
1:21:09 - Q8: Inner-sphere reorganization and proton transfer
1:23:06 - Q9: Kinetic isotope effect
1:26:25 - Q10: Long molecules near electrode surface


Second Part:
1:28:11 - Heterogeneous electrochemical PCET
1:28:41 - Proton discharge (Volmer reaction)
1:35:50 - Adiabatic models for Volmer reaction
1:39:38 - Vibrational nonadiabaticity
1:40:41 - Unified formulation for Volmer reaction
1:45:45 - Other aspects of PCET modeling
1:47:01 - Remaining challenges and future directions

Second Q&A:
1:49:43 - Q11: The role of input parameters for modeling
1:52:28 - Q12: Hydrogen evolution on Au
1:54:48 - Q13: Kinetic isotope effect
1:56:48 - Q14: Solvent dynamics contribution
1:58:27 - Comment from Rudolph Marcus
1:59:50 - Q15: Weighted density of states calculations
2:02:25 - Q16: Dielectric continuum model for Volmer reaction


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Abstract: 
Proton-coupled electron transfer (PCET) plays a vital role in a wide range of electrochemical processes. This talk will describe theoretical and computational methods that have been developed to study electrochemical PCET. Theoretical formulations for both homogeneous and heterogeneous electrochemical PCET provide analytical expressions for the rate constants and current densities as functions of applied potential. The quantum mechanical treatment of the transferring protons and inclusion of excited vibronic states are critical for describing experimental data, such as Tafel slopes and kinetic isotope effects. A variety of experimentally relevant applications will be discussed.