CuO/Cu(OH)₂ Heterostructure with Sustained Dynamic Re-equilibration and High HER Activity

Area of Science:

• Electrochemistry and Materials Science
• Catalysis for energy conversion

Background:

• Copper-based catalysts like CuO and Cu(OH)2 are effective for alkaline hydrogen evolution reaction (HER).
• Direct synthesis often leads to unstable architectures that degrade during operation.
• Need for robust and active electrocatalysts for efficient hydrogen production.

Purpose of the Study:

• To investigate copper sulfide (Cu2S) as a metastable precursor for generating stable and active HER electrocatalysts.
• To understand the electrochemical reconstruction mechanism of Cu2S into a dynamic CuO/Cu(OH)2 heterostructure.
• To evaluate the catalytic performance and stability of the reconstructed interface.

Main Methods:

• Utilized copper sulfide (Cu2S) as a precursor for electrochemical reconstruction.
• Employed combined ex situ and operando analyses (e.g., spectroscopy, microscopy) to study the transformation.
• Performed electrochemical measurements including overpotential, Tafel slope, and charge-transfer resistance.
• Conducted temperature-programmed desorption, Auger electron spectroscopy, and Raman isotope experiments.

Main Results:

• Cu2S rapidly reconstructs into a dynamic CuO/Cu(OH)2 heterostructure under alkaline HER conditions.
• The reconstructed interface exhibits a bias-stabilized dynamic steady state with continuous regeneration of Cu(OH)2.
• Enhanced HER activity was observed, with an overpotential of 70 mV at 10 mA cm-2 and a 40-fold reduction in charge-transfer resistance.
• Sustained activity and morphology were maintained over 138 hours of galvanostatic operation.

Conclusions:

• Copper sulfide (Cu2S) serves as an effective metastable precursor for self-regenerating oxyhydroxide electrocatalyst interfaces.
• Electrochemical bias stabilizes the dynamic CuO/Cu(OH)2 equilibrium, crucial for sustained catalytic performance.
• Provides mechanistic insights into designing nonequilibrium, water-mediated electrocatalysts for hydrogen evolution.