Bi-Zr-Modulated CO₂ Microenvironment Enables High-Rate CO₂ Electroreduction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Engineering the local chemical environment is key for electrochemical CO2 reduction reactions (CO2RR).
• Bismuth-zirconium composite catalysts (Bi-Zr-KB) were developed to modify the CO2 microenvironment in alkaline flow cells.

Purpose of the Study:

• To investigate the effect of zirconium incorporation on bismuth-based catalysts for CO2RR.
• To optimize the Bi/Zr ratio for enhanced catalytic performance and formate selectivity.

Main Methods:

• Synthesis of Bi-Zr-KB catalysts with varying Bi/Zr ratios.
• Electrochemical testing in an alkaline flow-cell system.
• Material characterization using XPS, SEM, EDX, XAS, EIS, and in-situ Raman spectroscopy.
• Density functional theory (DFT) calculations.

Main Results:

• The Bi-Zr-KB catalyst with a 2:1 Bi/Zr ratio achieved a current density of -176 mA cm⁻² and 88% formate Faradaic efficiency at -0.6 V.
• This represents a 1.4-fold performance enhancement compared to the bismuth-only catalyst.
• Zr incorporation suppressed local pH rise and improved CO2 availability, while DFT calculations indicated enhanced CO2 adsorption and charge transfer at interfacial Bi-Zr phases.

Conclusions:

• Zirconium incorporation effectively modulates the catalyst's microenvironment, overcoming CO2 mass transport limitations.
• Bi-Zr-KB catalysts offer a promising strategy for high-rate electrochemical CO2 conversion to formate.
• The study highlights the importance of interfacial engineering in catalyst design for CO2RR.