Developing Joule-heating regeneration of carbon-based adsorbents for Direct Air Capture

Abstract

As anthropogenic CO₂ emissions responsible for our changing climate continue to rise, new technologies are needed to reduce their impact. Direct Air Capture (DAC) is a developing technological solution whereby CO₂ is captured directly from ambient air and later released in a controlled manner for further use or storage. This work details the development of a new, simple methodology that allows DAC candidate materials to be tested quickly and reliably in real atmospheric conditions at lab-scale. Targeting facile and efficient initial materials screening the methodology presented uses Joule heating for material regeneration, a rapid heating technique we find can raise the temperature of activated carbon-based sorbents to over 100 °C in 10 s. Focussing on a KOH-impregnated activated‑carbon cloth (i-ACC-KOH) sorbent, we find a linear relationship between regeneration temperature and reversible CO₂ capacity, with a peak capacity of 100 ± 20 mmol kg⁻¹ in low-humidity atmospheric conditions. Performance under high-humidity and long cycling experiments were also assessed, highlighting key inputs in providing a well-rounded picture of material capability. We employ our methodology to demonstrate: (i), the rapid kinetics of our Joule heating methodology with only 20–25 min per cycle (5–10 min desorption, 15 min adsorption); (ii), the impact of ambient humidity on the performance of i-ACC-KOH, identifying only a limited reduction in capacity (≈ 8 %) with relative humidity up to 60 %; and (iii), high material stability with respect to cycling, retaining 80 % of capacity across 847 capture/release cycles. Overall, our work establishes a facile, lab-scale methodology for testing DAC sorbents in a Joule heating regeneration cycle, probing basic kinetics, competitive adsorption and cycling stability, and can facilitate the initial development of improved sorbents for DAC.