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Donor-Dependent Kinetics of Interfacial Proton-Coupled Electron Transfer
Megan N Jackson1, Yogesh Surendranath1
1Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
Journal of the American Chemical Society
|February 11, 2016
Summary
Proton donor structure significantly impacts electrocatalytic hydrogen evolution. Sterically hindered donors slow down concerted proton-electron transfer (CPET) on gold surfaces, affecting energy conversion efficiency.
Area of Science:
- Electrochemistry
- Surface Science
- Catalysis
Background:
- Interfacial concerted proton-electron transfer (CPET) is crucial for electrocatalytic energy conversion.
- Understanding the factors influencing CPET kinetics is essential for designing efficient catalysts.
Purpose of the Study:
- To investigate the effect of proton donor structure on interfacial CPET kinetics.
- To use hydrogen evolution reaction (HER) as a proxy for interfacial CPET rates on polycrystalline gold.
Main Methods:
- Studied hydrogen evolution rates using trialkylammonium donors with varying steric profiles but identical pKa.
- Conducted kinetic studies in acetonitrile and aqueous electrolytes.
- Analyzed transfer coefficients and H/D kinetic isotope effects.
Main Results:
- Triethylammonium (TEAH+) showed up to 20-fold faster CPET kinetics than diisopropylethylammonium (DIPEAH+) in acetonitrile.
- Steric effects were diminished in aqueous electrolytes, indicating water's mediating role.
- TEAH+ exhibited a higher transfer coefficient (β=0.7) and potential-dependent kinetic isotope effects compared to DIPEAH+ (β=0.4).
Conclusions:
- Proton donor structure profoundly influences the free energy landscape for CPET on solid surfaces.
- The proton donor plays a critical role in the kinetics of electrocatalytic energy conversion.
- Solvent effects, particularly water, can mitigate steric constraints in interfacial CPET.
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