Corrections to the terminology.

Proton coupled electron transfer (PCET), a chemical reaction that involves the transfer of electrons and protons from one atom to another.

PCET can proceed through three pathways.

CPET, Concerted Proton Electron Transfer.

PTET: Proton Transfer Electron Transfer

ETPT: Electron Transfer Proton Transfer.

You have to formulate your question using the correct terminology.

Yurii V Geletii Thank you for the comment. Accordingly, my concern is;

I am conducting DFT-based VASP calculations to study the non-concerted lattice oxygen mechanism (NLOM) for the oxygen evolution reaction (OER). In this mechanism, the proton and electron transfer steps are decoupled, unlike the concerted lattice oxygen mechanism (CLOM), where each reaction step involves coupled proton-electron transfer (CPET), typically referenced to the standard hydrogen electrode (SHE).

In the context of Proton Coupled Electron Transfer (PCET), the decoupling introduces two possible pathways:

This decoupling also introduces a dependency of the proton transfer step on the pH of the system. Could anyone guide me on how to theoretically calculate the Gibbs free energy for these decoupled proton and electron transfer steps? Specifically:

• How to account for the decoupling of proton and electron transfer (PTET and ETPT) in DFT calculations?
• How to incorporate the influence of pH on the proton transfer step in the Gibbs free energy calculations?

Build a square scheme for each single electron transfer and calculate the thermodynamic of three pathways.

Hi Beenish Ajmal

It's not so easy to treat ET and PT separately on a surface. In general, ET processes can be studied with ET theories, e.g. Marcus theory or it's extension - homogeneous PCET theory. Thermodynamics of the total process (ET/PT or PT/ET - doesn't matter) can be calculated using CHE (computational hydrogen electrode) model. If you compare the electronic coupling between the adsorbate and the metal surface and the vibronic coupling between the proton donor and acceptor, you can conclude whether you have a concerned or sequant mechanism (Article Calculation of Vibronic Couplings for Phenoxyl/Phenol and Be...

Or, you can use Grand Canonical DFT to conduct the constant-potential calculations, but as far as I know, it's not implemented in VASP. In this case, you'll explicitly get the free energies of both processes.

Liana

Liana Savintseva Thank you for sharing your experience. Are you working on the same research area? Which software do you suggest that is suitable for PT and ET calculations? Right now I am using VASP.

Best,

Beenish Bashir.

Beenish Ajmal Yes, I'm working in the same area of research, but more in organic electrochemistry, where the surface doesn't play a big role.

I know that the GC-DFT is implemented in GPAW code (Article Adiabatic versus non-adiabatic electron transfer at 2D elect...

I hope you find it useful.

Best,

Liana

Beenish Ajmal hi again!

I've just found a nice approach that may work better for your task since it's in VASP. The double reference method described here Article First-Principles Analysis of the Initial Electroreduction St...

In this approach, change the number of electrons with NELECT = number_of_electrons_from_outcar +- n (n can be any number) to create a charged simulation cell and apply IDIPOL = 3.

Best wishes,

Liana

Liana Savintseva Thank you very much for sharing the paper.

Best,

Beenish Ajmal.