Vacancy and doping engineering of Ni-based charge-buffer electrode for highly-efficient membrane-free and decoupled...

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Low-cost, large-scale hydrogen energy supply is crucial.
• Membrane-free water electrolysis presents significant challenges.
• Efficient hydrogen and oxygen production requires advanced electrode materials.

Purpose of the Study:

• To develop a membrane-free, two-step water electrolysis system.
• To decouple hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) temporally.
• To utilize cobalt-doped Ni(OH)2 nanosheets as charge mediators.

Main Methods:

• In-situ growth of metal-organic framework and alkali-etching technique to anchor Co-doped Ni(OH)2 nanosheets onto nickel foam.
• Electrochemical characterization of HER and OER processes.
• Assembly of a Ni-Zn battery for continuous hydrogen production without external power.

Main Results:

• Successfully demonstrated a membrane-free, two-step water electrolysis system.
• Achieved decoupled HER and OER with a Ni(OH)2/NiOOH charge mediator.
• Co-doping enhanced electrode conductivity, shifted redox potential, and improved OH- adsorption, boosting HER/OER activity.
• Ni-Zn battery integration enabled continuous H2 production coupled with battery discharge.

Conclusions:

• The developed decoupled water electrolysis device is a promising pathway for efficient renewable energy to hydrogen conversion.
• Cobalt doping significantly enhances the performance of the charge-buffer electrode for water electrolysis.
• This membrane-free approach offers a viable strategy for low-cost hydrogen production.