Carbon capture in polymer-based electrolytes

Abstract

Nanoparticle organic hybrid materials (NOHMs) have been proposed as excellent electrolytes for combined CO2 capture and electrochemical conversion due to their conductive nature and chemical tunability. However, CO2 capture behavior and transport properties of these electrolytes after CO2 capture have not yet been studied. Here, we use a variety of nuclear magnetic resonance (NMR) techniques to explore the carbon speciation and transport properties of branched polyethylenimine (PEI) and PEI-grafted silica nanoparticles (denoted as NOHM-I-PEI) after CO2 capture. Quantitative 13C NMR spectra collected at variable temperatures reveal that absorbed CO2 exists as carbamates (RHNCOO− or RR′NCOO−) and carbonate/bicarbonate (CO32−/HCO3−). The transport properties of PEI and NOHM-I-PEI studied using 1H pulsed-field-gradient NMR, combined with molecular dynamics simulations, demonstrate that coulombic interactions between negatively and positively charged chains dominate in PEI, while the self-diffusion in NOHM-I-PEI is dominated by silica nanoparticles. These results provide strategies for selecting adsorbed forms of carbon for electrochemical reduction.