Anomalous hydrogen evolution behavior in high-pH environment induced by locally generated hydronium ions

Area of Science:

• Electrocatalysis
• Nanomaterials Science
• Surface Chemistry

Background:

• Fundamental electrocatalysis studies often rely on bulk materials, whose mechanisms may not apply to nanostructured catalysts.
• Nanostructured electrocatalysts exhibit higher activity, but the underlying mechanisms in different environments are not fully understood.

Purpose of the Study:

• To propose an alternative reaction mechanism for nanostructured electrocatalysts, specifically for the hydrogen evolution reaction.
• To investigate the role of intermediates in high-pH electrolytes and explain the anomalous activity of nanomaterials.

Main Methods:

• In-situ Raman spectroscopy to identify reaction intermediates.
• Electrochemical thermal and kinetic measurements on various nanomaterials.
• Studies conducted in high-pH electrolytes to simulate conditions with low bulk hydronium (H3O+) concentration.

Main Results:

• Identification of massive hydronium (H3O+) intermediate generation on nanostructured catalytic surfaces during water dissociation and hydrogen adsorption.
• Observation of a localized acid-like environment created by these H3O+ intermediates.
• Demonstration that this localized environment significantly reduces the energy barrier for the hydrogen evolution reaction.

Conclusions:

• A novel reaction mechanism for nanostructured electrocatalysts in high-pH media is proposed, involving H3O+ intermediates.
• The generated H3O+ intermediates explain the anomalously high activity of nanostructured electrocatalysts in alkaline conditions.
• This finding offers new insights into designing efficient electrocatalysts for reactions like hydrogen evolution.