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In Situ EC-EPR Spectroscopy and DFT Analysis of HUPD on Polycrystalline Pt
Rainer Götz1, Kimmo Pyyhtiä2, Bingxin Li3
1Physics of Energy Conversion and Storage, TUM School of Natural Sciences, Department of Physics, Technical University of Munich, Garching, Germany.
Chemsuschem
|March 8, 2026
Summary
Investigating hydrogen adsorption on platinum surfaces using electron paramagnetic resonance (EPR) spectroscopy reveals key insights into active sites for hydrogen evolution and oxidation reactions, crucial for renewable energy catalysis.
Area of Science:
- Catalysis research
- Electrochemical energy conversion
- Surface science
Background:
- Electrochemical hydrogen production and conversion are vital for renewable energy.
- Platinum and its group metals are excellent catalysts for hydrogen evolution (HER) and oxidation (HOR) reactions.
- Understanding active surface sites is crucial for improving catalyst performance and fundamental knowledge, but challenging due to hydrogen's surface mobility.
Purpose of the Study:
- To elucidate the nature of active surface sites for hydrogen adsorption on platinum.
- To investigate hydrogen electrosorption in the underpotential deposition (UPD) region using in situ electron paramagnetic resonance (EPR) spectroscopy.
- To provide fundamental insights into hydrogen adsorption mechanisms relevant to HOR and HER.
Main Methods:
- In situ electron paramagnetic resonance (EPR) spectroscopy was employed to study platinum surfaces in acidic media during hydrogen underpotential deposition (H-UPD).
- Ab initio molecular dynamics (AIMD) and density functional theory (DFT) calculations were performed to model hydrogen adsorption on platinum surfaces.
- Correlating EPR signals with theoretical predictions to identify preferred hydrogen adsorption sites.
Main Results:
- EPR measurements indicated hydrogen adsorption sites on platinum, with maximum signal intensity at -0.85 V versus Pt, vanishing before HER.
- Theoretical calculations suggest that atomic hydrogen preferentially adsorbs on-top or 3-fold hollow sites, with bridge sites being unlikely.
- DFT calculations at high hydrogen coverage (7/12 ML) favored fcc hollow sites (0.72 probability) over on-top sites (0.26 probability), consistent with EPR observations.
Conclusions:
- EPR spectroscopy successfully probed hydrogen adsorption sites on polycrystalline platinum in the H-UPD region, marking a novel application in this field.
- The study identified on-top and 3-fold hollow sites as the primary adsorption locations for atomic hydrogen on platinum surfaces.
- Findings contribute to a better understanding of catalytic mechanisms in electrochemical hydrogen reactions, guiding the development of improved catalysts.
