Synergetic Control of Single-Molecule Proton Transfer: Electrode Geometry Meets Solvent Proton Activity

Area of Science:

• Surface Science
• Physical Chemistry
• Molecular Electronics

Background:

• Proton transfer on solid surfaces is crucial for catalysis, molecular electronics, and biology.
• Elucidating proton transfer mechanisms at interfaces is challenging due to electrode dynamics and aqueous environments.

Purpose of the Study:

• To investigate the interplay between proton concentration and electrode configuration in regulating interfacial proton transfer.
• To understand the factors influencing the single-molecule conductance of octanedioic acid.

Main Methods:

• Combined scanning tunneling microscope break junction (STM-BJ) experiments and density functional theory (DFT) calculations.
• Utilized ab initio molecular dynamics (AIMD) simulations to study electrode structural evolution.

Main Results:

• DFT calculations reproduced experimental high- and low-conductance plateaus.
• Hydrogen-bonded water networks and diatomic sites promote carboxyl deprotonation.
• Electrode terminal evolution (diatomic to monatomic) during stretching induces a deprotonation-to-protonation transition, observed as a two-step plateau.

Conclusions:

• Established a framework linking proton concentration, interfacial proton transfer kinetics, and single-molecule conductance.
• Provided fundamental insights for designing electrochemical interfaces and devices.
• Demonstrated the critical role of electrode configuration and proton concentration in interfacial proton transfer.