Carbon fabrics for electrified direct air capture: From substrate morphology to module-scale operating trade-offs

[Geoengineering News]

https://www.sciencedirect.com/science/article/pii/S1385894726066994

Authors: Carla Esch, Jacqueline Kieven, Antonia Geiser, Roman Ryapushkin, Wibke Zängle, Matthias Wessling

16 July 2026

Highlights

•Comparison of macroporous and microporous carbon fabrics as electrified DAC sorbents.

•Utilization of only 15–30 % of intrinsic sorbent capacity under continuous flow.

•Tuning of CO2 breakthrough and product concentration through PEI loading and flow rate.

•Enhancement of CO2 capture through water-induced PEI swelling under humid operation.

•Interplay of substrate, coating, and operating parameters shapes DAC performance.

Abstract

Polyethyleneimine (PEI)-impregnated carbon fabrics are structured direct air capture (DAC) sorbents whose electrical conductivity enables resistive temperature swing regeneration. However, how substrate morphology translates intrinsic sorbent properties into module-scale DAC performance under continuous flow remains poorly understood. We investigate this using a resistively heated spiral wound module (SWM). Two carbon fabrics, a macroporous non-woven (E20) and a microporous activated carbon cloth (FM10), were characterized. Thermogravimetric analysis revealed a trade-off between CO2 capacity and kinetics: higher PEI loading enhanced capacity but slowed sorption and desorption. FM10 showed faster kinetics than E20, yet its higher surface area did not increase CO2 uptake, indicating that accessibility rather than amine content governed the usable capacity. The kinetically favorable FM10 was deployed in the SWM under DAC-relevant conditions (400 ppm CO2). Comparison of intrinsic and dynamic performance revealed that only 15-30 % of the intrinsic capacity was utilized under continuous-flow operation, demonstrating that DAC performance is governed by transport limitations rather than equilibrium sorbent properties alone. Reducing gas flow rate improved dynamic yield at the expense of productivity. Humid operation enhanced yield through water-induced PEI swelling while reducing the specific regeneration energy. This energy was dominated by parasitic heat loss rather than by the sorbent, identifying module heat management, alongside dynamic utilization, as a design-limited lever. These results show that the dominant challenge in electrified DAC is not maximizing intrinsic sorbent capacity, but maximizing its dynamic utilization through the coupled design of substrate morphology, PEI distribution, module architecture, and operating strategy.

Source: ScienceDirect