Introduction of the SiO₂ Buffer Layer Enables High CO Selectivity in Bicarbonate Electrolyzer

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• Liquid-phase bicarbonate electrolyzers are energy-efficient alternatives to gas-fed systems.
• Intense hydrogen evolution reaction (HER) significantly competes with CO2 reduction in these systems.

Purpose of the Study:

• To suppress hydrogen evolution reaction (HER) in cation exchange membrane bicarbonate electrolyzers.
• To enhance CO2 electroreduction efficiency using an interfacial modulation strategy.

Main Methods:

• Introducing a thin SiO2 buffer layer onto the catalyst surface.
• Optimizing KHCO3 concentration and utilizing a hydrophilic carbon paper substrate.
• Investigating interfacial effects on H+ and HCO3- transport.

Main Results:

• The SiO2 buffer layer effectively suppressed HER by restricting H+ transport.
• Achieved 89% CO Faradaic efficiency at 50 mA cm-2.
• Enhanced CO partial current density by 2.8-fold to 125 mA cm-2 at 250 mA cm-2.

Conclusions:

• Interfacial modulation with a SiO2 buffer layer is a viable strategy to improve CO2 electroreduction.
• The strategy shows broad applicability to various catalysts (Ag, CoPc@CNT).
• Highlights potential for integrated CO2 capture and electroreduction technologies.