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Active Phase of Nickel Electrocatalysts Driving Alkaline Hydrogen Evolution
Yifeng Wang1, Eleanor Ender2,3, Santosh Kumar4
1Department of Materials, Imperial College London, London, U.K.
Advanced Materials (Deerfield Beach, Fla.)
|August 13, 2026
Summary
Understanding nickel/oxo-hydroxo interfaces is key for efficient hydrogen evolution. Mild anodic pre-conditioning boosts activity by regenerating active subsurface species, crucial for durable alkaline water electrolysis cathodes.
Area of Science:
- Electrochemistry
- Materials Science
- Surface Science
Background:
- Nickel-based cathodes are vital for alkaline water electrolysis.
- The active surface chemistry and stability of these cathodes under operating conditions are not fully understood.
- The role of metal/oxo-hydroxo interfaces in hydrogen evolution reaction (HER) activity requires clarification.
Purpose of the Study:
- To investigate the dynamic evolution of Ni/NiOxHy interfaces during the hydrogen evolution reaction.
- To elucidate the role of metal/oxo-hydroxo interfacial structures in governing HER activity.
- To establish a framework for designing robust HER cathodes.
Main Methods:
- Operando Ni L-edge X-ray absorption spectroscopy (XAS)
- Depth-sensitive XAS (total electron yield and Auger electron yield modes)
- X-ray photoelectron spectroscopy (XPS)
- Isotopically labeled nano secondary ion mass spectrometry (NanoSIMS)
- Online electrochemical mass spectrometry (OEMS)
- Utilized well-defined sputtered Ni thin films as a model system.
Main Results:
- Progressive reduction of near-surface oxide/hydroxide species correlates with a loss of HER activity.
- Depth-resolved measurements show a metallic outermost surface under cathodic bias, with NiOxHy forming upon relaxation.
- Mild anodic pre-conditioning regenerates subsurface NiOxHy, leading to sustained HER activity enhancement.
Conclusions:
- Metal/oxo-hydroxo interfaces are crucial active phases for hydrogen evolution.
- The dynamic interplay between metallic Ni and NiOxHy governs HER performance.
- This study provides insights for engineering durable, high-performance HER cathodes for real-world electrolysis.
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