It is widely recognized that CO₂ is one of the driving forces behind the climate change. However, CO₂ is also a valuable resource for the formation of industrially relevant chemicals, and thus carbon capture and utilization, especially its electrical conversion, is becoming increasingly important. A major challenge for electrochemical fixation of CO₂ is the low energy efficiency of electrocatalysts due to high overpotentials. A cost-effective and sustainable material in the field of CCU is nitrogen-rich polymers such as polyethyleneimine (PEI) [1] or polyimidazolium (PI). These polymers are particularly well suited for CO₂ adsorption at low partial pressures, which would allow for the direct utilization of industrial flue gas. However, they lack the necessary electrical conductivity. Therefore, the design of hybrid materials combining porous carbons with high electrical conductivity and the CO₂-absorbing polymer is key. In this work, these nitrogen-rich polymers were incorporated into carbon substrates via a sonication-assisted impregnation process to improve transport properties and conductivity, both of which are important for subsequent electrochemical CO₂ conversion.

The pristine mesoporous carbon substrate was synthesized via zinc oxide-templated carbonization of sucrose at 950 °C and exhibits a specific BET surface area of 1750 m²/g, a high pore volume of 3 cm³/g as well as a hierarchical pore system [2]. These polymer-carbon composites have been characterized by physisorption measurements (N₂/CO₂), thermal response measurements (Infrasorp) and DRIFTS. All these measurements indicate a strong interaction of these polymer-carbon composites with CO₂ even at low pressures. By using a highly porous carbon support matrix, the initial CO₂ uptake is increased at least 10-fold compared to the bulk polymer. In addition, the irreversibility of CO₂ adsorption is proposed to follow a chemisorption mechanism and thus activate the CO₂ molecule.

First electrochemical measurements were performed on a rotating ring-disk electrode (RRDE). The results exemplify how the material can be used as an electrocatalyst for the reduction of CO₂. These hybrids were found to exhibit significant selectivity between the hydrogen evolution reaction (HER) and the CO₂ reduction reaction (CO2RR), as no hydrogen was detected in CO₂-saturated KHCO₃ solutions. It is anticipated that, due to their enhanced affinity for CO₂, a selective conversion process can be achieved without the need for metallic catalyst centers. Current work aims at transitioning from these fundamental RRDE investigations to more application-oriented measurements in a GDE/zero gap setup [3]. The goal is to enhance the faradaic efficiency further towards CO formation under flue gas conditions by using diluted CO₂ as a feed gas.