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Published on: March 29, 2016
Disentangling Multiple pH-Dependent Factors on the Hydrogen Evolution Reaction at Au(111)
Er-Fei Zhen1, Bing-Yu Liu1, Meng-Ke Zhang1
1Hefei National Research Center for Physical Sciences at Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China.
Precision Chemistry
|March 28, 2025
Summary
Electrolyte pH significantly impacts electrocatalytic activity, but electric double layer (EDL) effects complicate analysis. Correcting for EDL factors reveals that intrinsic hydrogen evolution reaction (HER) kinetics are only weakly pH-dependent.
Area of Science:
- Electrochemistry
- Surface Science
- Physical Chemistry
Background:
- Electrolyte pH is critical for electrocatalytic activity.
- pH effects are complex due to simultaneous changes in driving forces and reactant concentrations within the electric double layer (EDL).
Purpose of the Study:
- To disentangle pH-dependent factors affecting electrocatalysis.
- To investigate the hydrogen evolution reaction (HER) at Au(111)-aqueous solution interfaces as a model system.
Main Methods:
- Utilized the hydrogen evolution reaction (HER) on Au(111) as a model system.
- Developed a reaction model accounting for local conditions within the EDL.
- Analyzed HER current densities across different pH values (0.1 M NaOH vs. 0.1 M HClO4).
Main Results:
- HER current density varied up to 60-fold between acidic and basic electrolytes.
- After correcting for EDL effects, the intrinsic rate constant for HER showed only weak pH dependence.
- The primary cause of observed pH effects was identified as pH-dependent reorganization free energy.
Conclusions:
- Observed pH effects in electrocatalysis are largely artifacts of EDL conditions.
- Intrinsic kinetic pH dependence is minimal once EDL effects are accounted for.
- Understanding intrinsic kinetics requires correction for EDL electrostatic potential and local reactant concentrations.
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