Surface Chemistry of WC Powder Electrocatalysts Probed In Situ with NAP-XPS
Christoph Griesser1, Sergio Diaz-Coello1, Matteo Olgiati2
1Department of Physical Chemistry, University of Innsbruck, Innrain 52 c, Innsbruck, 6020, Austria.
Angewandte Chemie (International Ed. in English)
|March 17, 2025
Summary
Tungsten carbide (WC) shows high activity for hydrogen evolution reaction (HER) catalysis. In situ electrochemical X-ray photoelectron spectroscopy (EC-XPS) reveals that its oxide layer dissolves during HER in alkaline media, clarifying the active surface.
Area of Science:
- Materials Science
- Electrochemistry
- Surface Chemistry
Background:
- Tungsten carbide (WC) is recognized for its high electrocatalytic activity in water splitting, particularly the hydrogen evolution reaction (HER).
- WC's susceptibility to oxidation and potential passivation raises questions about the fundamental reasons for its catalytic performance, especially under reaction conditions.
Purpose of the Study:
- To investigate the surface chemistry of tungsten carbide (WC) electrodes during the hydrogen evolution reaction (HER) in an alkaline electrolyte.
- To elucidate the active surface termination responsible for WC's high electrocatalytic activity under operating conditions using in situ techniques.
Main Methods:
- Electrochemical X-ray Photoelectron Spectroscopy (EC-XPS) was employed to analyze the surface chemistry of WC powder electrodes.
- In situ measurements were performed under full potential control in an alkaline electrolyte to mimic actual HER conditions.
Main Results:
- The WC electrode surface, initially covered by an oxide layer, was observed to undergo dissolution of this passive film.
- This dissolution occurs under electrochemical reaction conditions, revealing the active surface termination during the HER.
Conclusions:
- The study clarifies that the active surface for HER on WC in alkaline media is not the initial oxide layer but is exposed after its dissolution.
- Electrochemical X-ray Photoelectron Spectroscopy (EC-XPS) is demonstrated as a valuable tool for studying the surface chemistry of applied energy conversion materials under realistic operating conditions.
