Isopotential Electron Titration: Hydrogen Adsorbate-Metal Charge Transfer

Area of Science:

• Surface Science
• Catalysis
• Electrochemistry

Background:

• Charge transfer at the adsorbate-thermocatalytic surface interface is crucial for catalytic activity.
• Direct, quantitative measurement of this charge transfer has been a significant challenge in surface science.

Purpose of the Study:

• To introduce and validate a novel method, isopotential electron titration (IET), for directly quantifying charge transfer between adsorbates and catalytic surfaces.
• To investigate the charge transfer dynamics between adsorbed hydrogen and a platinum (Pt) surface.

Main Methods:

• Utilized a catalytic condenser setup with a Pt surface, a p-type silicon layer, and a hafnia dielectric film.
• Achieved isopotential conditions between Pt and Si layers to titrate adsorbate-surface charge transfer via an external circuit.
• Employed Bader charge analysis for theoretical validation of experimental results.

Main Results:

• Demonstrated that adsorbed hydrogen atoms donate electrons to the Pt surface upon adsorption, with this transfer being reversible upon desorption.
• Quantified the charge transferred to Pt by an adsorbed hydrogen atom as 0.19 ± 0.01% |e|/H across temperatures of 125-200 °C.
• Experimental findings were corroborated by Bader charge analysis, indicating a net donation of 0.4% |e|/H.

Conclusions:

• Isopotential electron titration (IET) provides a direct, quantitative, and electronic-based method for characterizing catalytic surfaces and adsorbed species.
• This technique enables a deeper understanding of the electronic interactions governing catalytic reactions.
• The study opens avenues for precise electronic characterization of catalytic materials and reaction mechanisms.