Direct air capture (DAC) has emerged as a pivotal technology for mitigating global CO₂ emissions and achieving NetZero by 2050. Established DAC technologies typically employ alkanolamine or aqueous alkaline absorbents for CO₂ capture, yet they incur high capital and operation costs^1-3. These methods necessitate thermal cycling for CO₂ capture and absorbent regeneration, exacerbating the process's carbon footprint. For example, thermal cycling process for alkaline absorbents alone incurs an energy cost of approximately 8 GJ/tCO₂¹.

The electrochemical DAC (eDAC) system offers a distinct approach to CO₂ capture and absorbent regeneration at a lower energy cost. Electrochemical capture methods commonly employ either organic or inorganic capture species^4,5. While the inorganic strategy using alkali hydroxide absorbents enables stable atmospheric CO₂ capture and release, it often demands a high energy cost (6–10 GJ/tCO₂). Conversely, employing organic molecules has shown relatively lower energy consumption for electrochemical CO₂ capture and release methods. However, the functional groups of such organic molecules are susceptible to oxidation by atmospheric oxygen (O₂), particularly at DAC conditions where the O₂ concentration exceeds that of CO₂ by 500-fold.

Here, we present a hybrid approach that achieves stable and efficient atmospheric CO₂ capture and release using alkali hydroxide absorbents (KOH) and organic redox mediators (Fig. 1, RM). This strategy combines the durability of alkali hydroxide capture absorbents with the fast kinetics of organic redox-active mediators. Employing a two-electrolyser electrocatalysis system, we operate the hydrogen evolution reaction (HER) in one electrolyser to generate OH^- for CO₂ capture, and the hydrogen oxidation reaction (HOR) in another electrolyser to generate H⁺ for CO₂ release. The organic RM is oxidized and reduced at the counter electrode of the HER and HOR, respectively. With this approach, we achieve a minimum work of 0.82 GJ/tCO₂, calculated based on the cyclic voltammetry redox potentials, and as low as 3.8 GJ/tCO₂ in a practical two-electrolyser configuration with over 200 hours of stable operation.

Additionally, we introduce a new air contactor design that harnesses ambient wind to capture CO₂ in the form of solid K₂CO₃ precipitates using a KOH solution and carbonate crystallizer. We demonstrate high-rate DAC capabilities of our carbonate crystallizer that are pertinent to large-scale industrial deployment, achieved without the need for costly equipment such as fans, packing, pumps, and the associated complex system designs. This approach yields a significant reduction in both capital and operation cost of the eDAC system.