Interfacial Field-Driven Proton-Coupled Electron Transfer at Graphite-Conjugated Organic Acids

Area of Science:

• Surface chemistry
• Electrochemistry
• Computational materials science

Background:

• Interfacial proton-coupled electron transfer (PCET) reactions are vital for energy conversion technologies.
• Molecular-level understanding of interfacial PCET at carbon surfaces is limited.
• Graphite-conjugated catalysts (GCCs) with organic acid functional groups offer designer sites for interfacial PCET.

Purpose of the Study:

• To compute and analyze interfacial electrostatic potentials and electric fields at GCC organic acids.
• To investigate the factors governing proton-coupled redox potentials at GCCs.
• To elucidate the role of conjugation and electronic coupling in interfacial PCET.

Main Methods:

• Computational modeling of interfacial electrostatic potentials and electric fields.
• Calculation of proton-coupled redox potentials for GCCs.
• Comparison of theoretical results with cyclic voltammetry measurements.

Main Results:

• Computed redox potentials for GCCs agree with experimental cyclic voltammetry data.
• Trends in redox potentials correlate with molecular acidity and graphite conjugation.
• Interrupted conjugation in GCC acetic acid explains the absence of a PCET peak.

Conclusions:

• Continuous conjugation and strong electronic coupling are essential for interfacial field-driven PCET at GCC acid sites.
• Understanding surface atomic structure-electrostatic potential relationships can guide heterogeneous catalyst design.
• This study provides critical molecular-level insights into interfacial PCET mechanisms.