Direct air capture and CO2 conversion will play vital roles in a future circular carbon economy. Here, we propose a novel system for integrated CO2 capture and conversion through the combined use of solid and liquid sorbents and demonstrate its technical feasibility. CO2 is initially captured from the air using an amine-functionalized solid sorbent that is regenerated by rinsing with an aqueous carbonate-rich solution. The resulting bicarbonate-rich solution is fed to an electrolyzer, converting the bicarbonate electrolyte to syngas. Through our experiments, we demonstrate that the dual-sorbent system is capable of capture from air as well as solid sorbent regeneration and CO2 conversion. We use a simplified process model based on experimental results to explore the effects of scaling the components of the proposed system. We find that the pH-swing between the rich and lean solutions is a dominant design parameter, which is almost exclusively governed by the electrolyzer sizing. A small pH swing results in an improved electrolyzer performance and beneficial syngas composition, whereas a large pH swing results in efficient solid sorbent use and decreased water loss. Our results further highlight the fundamental trade-offs that are present when designing integrated capture and conversion systems.
Burgers et al. (Wed,) studied this question.