Electrolyte-Electrocatalyst Interfacial Effects of Polymeric Materials for Tandem CO₂ Capture and Conversion...

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• Integrating CO2 capture and electrochemical conversion offers a pathway to reduce energy demands for CO2 regeneration, especially when powered by renewable electricity.
• Polyethylenimine (PEI)-based materials are effective CO2 sorbents and have shown promise in reactive capture processes, improving CO2 loading and influencing product selectivity and formation rates compared to traditional aqueous electrolytes.
• The specific effects of PEI-based electrolytes on the catalyst-electrode interface during electrochemical CO2 reduction (CO2R) remain poorly understood.

Purpose of the Study:

• To investigate the impact of PEI-based electrolytes on the morphology and nanomechanical properties of a silver electrode during electrochemical CO2 reduction (CO2R).
• To utilize in situ electrochemical atomic force microscopy (EC-AFM) to probe the dynamic behavior of the PEI-electrode interface.
• To understand how electrolyte composition, CO2 loading, and PEI molecular weight influence the near-electrode environment and its implications for CO2R.

Main Methods:

• Preparation of PEI-based electrolytes.
• In situ electrochemical atomic force microscopy (EC-AFM) to study the nanomechanical properties (DMT modulus) of a silver electrode surface during CO2R.
• Analysis of PEI chain reorganization under applied negative polarization, varying electrolyte composition (including KHCO3) and CO2 capture levels, and using different PEI molecular weights.

Main Results:

• Distinct nanomechanical properties of PEI on the electrode surface were identified using EC-AFM.
• Negative polarization induced PEI chain reorganization due to electrostatic interactions, with changes dependent on electrolyte composition and CO2 loading.
• Higher CO2 loading and the presence of KHCO3 salt minimized PEI reorganization and alignment. PEI molecular weight also influenced the reconfiguration dynamics.

Conclusions:

• The near-electrode environment during CO2R is significantly influenced by the choice of polymer (PEI), electrolyte composition, and the amount of captured CO2.
• These factors critically impact the performance of electrochemical CO2 reduction.
• EC-AFM is demonstrated as a valuable tool for investigating the dynamic interfacial behavior during electrocatalysis.