Creating a Microenvironment in an Amine Solution for Integrated CO2 Capture and Electroreduction

Abstract

Integrated CO₂ capture and electrochemical utilization (ICCU) is promising for decarbonization by bypassing energy-intensive desorption/compression steps compared to conventional CO₂ capture and utilization (CCU) systems. However, the critical barrier in ICCU is the mass transfer limitations of carbon-containing species from amine solutions to electrode surfaces, leading to a low CO₂ conversion and a high hydrogen evolution reaction (HER). To address this issue, we introduce an interfacial engineering strategy to create a microenvironment using quaternary ammonium cationic surfactants for enhanced CO₂ conversion. In the cetyltrimethylammonium bromide (CTAB)-modified monoethanolamine (MEA) system, a Ag nanoparticle achieved 63.4% CO Faradaic efficiency at −0.82 V vs RHE, representing a 4.7-fold improvement over unmodified system. Chain-length optimization revealed that short-chain surfactants lacked sufficient hydrophobicity, while long-chain variants increased the mass transfer resistance, positioning CTAB (C₁₆) as the optimal candidate. The strategy demonstrates amine versatility and 50 h of recyclability without catalyst/amine degradation. In situ spectra and density functional theory calculation elucidated that CTAB has dual roles, i.e., CTAB cation (CTA⁺) adsorption repels the aggregation of protonated amine (MEAH⁺) on the electrode surface and the hydrophobic alkyl chains enrich the carbon-containing species. This work provides a mechanistic framework for designing efficient and stable ICCU systems through creating a microenvironment.