Hydride Formation and Decomposition on Cu(111) in HClO₄.

Area of Science:

• Electrochemistry
• Surface Science
• Catalysis

Background:

• Copper electrodeposition and hydrogenation catalysis involve complex interactions with adsorbed hydrogen.
• Understanding surface hydride formation and decomposition is crucial for optimizing these processes.

Purpose of the Study:

• To investigate the formation and decomposition of surface hydride on Cu(111) in HClO4 using electrochemical mass spectrometry.
• To correlate potential-dependent hydrogen adsorption and surface reconstruction with catalytic activity.

Main Methods:

• Electrochemical mass spectrometry (EC-MS) for in-situ analysis.
• Voltammetry and chronoamperometry to study potential-dependent phenomena.
• Analysis of hydrogen adsorption (Hads) coverage and surface reconstruction.

Main Results:

• Hydride formation is linked to two reduction waves, indicating potential-dependent Hads coverage.
• A 2D surface hydride exhibits distinct oxidative and reductive features around -0.05 V vs RHE.
• Extended negative potentials increase Hads coverage and reconstruction, accelerating hydride decomposition.
• Hads coverage reaches ~0.75 ML between -0.225 V and -0.275 V vs RHE, with further increases during hydrogen evolution reaction (HER).
• Hydride decomposition initiates above -0.05 V vs RHE, with H2 recombination and H3O+ oxidation as primary pathways.

Conclusions:

• Potential-dependent Hads coverage and surface reconstruction on Cu(111) influence hydride stability and decomposition.
• Strongly adsorbing anions (sulfate, halides) promote hydride decomposition via recombination, unlike perchloric acid.
• Results align with computational and STM studies, providing insights into copper-catalyzed hydrogenation.