Highly Selective Electrochemical Bicarbonate Conversion across C₁ and C₂ Products by Interface-Modulation with a...

Area of Science:

• Electrochemistry
• Carbon Capture and Utilization
• Materials Science

Background:

• Electrochemical reactive carbon capture (eRCC) faces performance limitations in conventional membrane electrode assembly (MEA) configurations due to coupled reaction steps.
• The zero-gap MEA interface detrimentally couples CO2 desorption, mass transport, and conversion, hindering efficient carbon utilization.

Purpose of the Study:

• To develop a novel electrochemical system that decouples the key steps in eRCC.
• To improve CO2 conversion efficiency, product selectivity, and system stability compared to traditional MEA setups.

Main Methods:

• Implementation of a three-compartment flow cell (3CFC) with a dedicated stripping compartment.
• Modulation of pressure differentials to direct CO2 transport and decouple mass transport from conversion.
• In situ/operando Raman spectroscopy to analyze interfacial pH and reaction mechanisms.
• Testing diverse catalysts (Cu(OH)2-derived, Ag electrodes, Ni single-atom-catalyst) for bicarbonate conversion.

Main Results:

• The 3CFC platform effectively decouples CO2 mass transport and conversion, enhancing eRCC performance.
• Unprecedented C2+ selectivity of 52.0% achieved with a Cu(OH)2-derived catalyst at -200 mA/cm2, a 17-fold increase from MEA.
• Ag electrodes demonstrated long-term stability (>155 h) in bicarbonate conversion, unlike MEA configurations.
• CO selectivity dramatically enhanced to 96.7% for a Ni single-atom-catalyst using 3CFC, compared to 38.0% in MEA.

Conclusions:

• The developed 3CFC presents a new principle for controlling interfacial chemical environments in electrochemical systems.
• This approach significantly enhances selectivity and stability for electrochemical reactive carbon capture and utilization.
• The 3CFC system offers a promising pathway for efficient and selective conversion of CO2.