Amorphous Phosphates Tailor Local Proton Supply for Alkaline Hydrogen Evolution Electrocatalysis.

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Alkaline water electrolysis is a cost-effective method for hydrogen (H2) production, avoiding noble metals and proton exchange membranes.
• However, the lack of protons in alkaline solutions hinders efficient hydrogen evolution reaction (HER) kinetics, even with active catalysts like cobalt phosphide (CoP).
• Excessive local acidity can cause catalyst corrosion and active site blockage.

Purpose of the Study:

• To develop a novel catalyst for improved hydrogen evolution reaction (HER) performance in alkaline media.
• To investigate a proton supply design principle for optimizing HER kinetics.
• To explore the functional roles of a cobalt phosphate coating on a CoP catalyst.

Main Methods:

• Fabrication of a "cobalt phosphate-clothed-CoP (CoPi@CoP)" nanoarray catalyst.
• Electrochemical characterization of the catalyst's hydrogen evolution reaction (HER) performance.
• In-situ analysis using differential mass spectrometry and spectroscopy.
• Electrochemical impedance spectroscopy and dynamic potential decay transients.
• Density functional theory (DFT) calculations for mechanistic insights.

Main Results:

• The CoPi@CoP catalyst demonstrated state-of-the-art HER performance in alkaline electrolytes, outperforming the base CoP catalyst.
• The amorphous cobalt phosphate (CoPi) layer facilitated water dissociation, buffered protons, and enhanced proton transfer.
• Mechanistic studies revealed the atomic-scale processes contributing to the improved HER activity.

Conclusions:

• The CoPi@CoP nanoarray catalyst effectively addresses the challenge of proton supply in alkaline HER.
• The developed proton supply design principle offers a new strategy for enhancing electrocatalytic water splitting.
• This work paves the way for more efficient and cost-effective hydrogen production via alkaline water electrolysis.