Direct Air Electrowinning

Direct Air Electrowinning (DAE) is an emerging class of technology that integrates direct air capture (DAC) of carbon dioxide (CO₂) with an electrochemical conversion process, such as electrowinning or CO₂ electrolysis.^[1][2] The core concept is to capture CO₂ directly from the atmosphere, and then, without intermediate purification or concentration steps, use renewable electricity to convert the captured CO₂ into valuable chemicals or fuels.^[1][3] This approach is a form of carbon capture and utilization (CCU) aimed at creating a circular carbon economy by transforming an atmospheric greenhouse gas into a feedstock for industrial processes.^[4]

The process usually has two main stages:

1. Capture: CO₂ is absorbed from the ambient air, often using an alkaline solution (like potassium hydroxide) to form a carbonate or bicarbonate solution.^[1][5]
2. Conversion: The resulting carbonate-rich solution is fed directly into an electrolytic cell. Here, an electric current drives chemical reactions that reduce the CO₂ into products like carbon monoxide (CO), formic acid, ethylene, or syngas, while regenerating the original capture solution.^[1][6]

Direct air electrowinning aims to overcome the high energy and cost barriers associated with traditional DAC, where captured CO₂ must be purified and compressed before utilization.^[2][7]

Direct air capture (DAC) is a technology designed to extract CO₂ directly from the ambient atmosphere, as opposed to capturing it from a point source like a factory flue stack.^[8] DAC systems typically use one of two main approaches:

• Liquid DAC: Air is passed through an aqueous alkaline solution, such as potassium hydroxide or sodium hydroxide, which reacts with and traps the CO₂.^[9][5]
• Solid DAC: Air is passed over solid sorbent materials that chemically bind with CO₂.^[9]

In the context of direct air electrowinning, liquid DAC systems are often preferred because the resulting carbonate solution can be used directly as the electrolyte in the subsequent electrochemical conversion step, avoiding the energy-intensive process of releasing the CO₂ as a pure gas.^[1] The main challenge for DAC is its high cost and energy consumption, stemming from the low concentration of CO₂ in the atmosphere (about 420 parts-per-million as of 2024).^[9]

Electrolysis is a process that uses direct electric current to drive a non-spontaneous chemical reaction. When applied to CO₂, it is known as CO₂ electrolysis or the CO₂ reduction reaction (CO2RR). In this process, CO₂ (often dissolved in a solution) is reduced at the cathode to form various chemical products. The specific product depends on the catalyst, electrode material, and operating conditions (voltage, temperature, pressure).^[4]

The term electrowinning traditionally refers to the extraction of metals from a leach solution.^[10] In the context of CO₂ conversion, its principles are adapted to "win" carbon-based products from the capture solution. The process can produce valuable chemicals like:

• Carbon monoxide (CO)
• Formic acid (HCOOH)
• Ethylene (C₂H₄)
• Ethanol (C₂H₅OH)
• Syngas (a mixture of CO and H₂)^[11][12]

When powered by renewable electricity, CO₂ electrolysis can produce carbon-neutral fuels and chemical feedstocks, creating a pathway to decarbonize industries like chemicals and transportation.^[4][11]

The innovation of direct air electrowinning lies in coupling the capture and conversion steps into a single, continuous process.^[1][3] Research has demonstrated that it is possible to take an alkaline solution used to capture CO₂ from the air and feed it directly into a zero-gap flow electrolyzer.^[13]

Key benefits of this integrated approach include:

• Energy Efficiency: It avoids the energy-intensive thermal or vacuum-swing processes typically required to release pure CO₂ from the capture medium. This is a major bottleneck in traditional DAC systems.^[2]
• Cost Reduction: By eliminating the CO₂ regeneration, purification, and compression steps, the integrated process has the potential to significantly lower both the capital and operational costs of carbon capture and utilization.^[3]
• Location Independence: Like all DAC technologies, these systems can be located anywhere, ideally co-located with abundant renewable energy sources like solar or wind farms, rather than being tied to a point source of emissions.^[8][3]
• Production of Valuable Goods: The process converts atmospheric CO₂, a waste product, into valuable chemical feedstocks, creating an economic incentive for carbon dioxide removal.^[4][12]

Direct air electrowinning is an active area of research, with several projects demonstrating its feasibility and working to improve its efficiency and scalability.

A 2022 study successfully demonstrated the concept by capturing CO₂ from the air in a potassium hydroxide solution and then converting the resulting (bi)carbonate solution into formate and carbon monoxide using a zero-gap flow electrolyzer with tin-based and silver-based catalysts, respectively.^[1] The study highlighted that integrating the capture and conversion steps is a crucial step toward the economic feasibility of CCU technology.^[7]

A notable example of this technology in development is the Air2Chem project, a collaboration between the Fraunhofer Institute UMSICHT, RWTH Aachen University, and several industry partners.^[6] Launched in 2024, the project aims to develop an economical, integrated process to convert atmospheric CO₂ into platform chemicals like ethylene and syngas.^[14] The process uses a membrane-based gas absorption system for DAC, coupled directly with carbonate electrolysis.^[3]

In 2025, the project reported positive interim results, including the successful testing of membranes for the DAC process and the identification of promising electrode materials and catalysts for the electrolysis step.^[3][15] The goal of Air2Chem is to develop a platform technology that can be piloted and eventually integrated into existing chemical industry infrastructures.^[6]

Despite its promise, the technology faces several challenges. The efficiency of the electrochemical conversion of CO₂ from (bi)carbonate solutions can be limited by competing reactions, such as the hydrogen evolution reaction (HER), which reduces water instead of CO₂.^[1] Improving the selectivity and activity of catalysts is therefore a key area of research.^[11]

Furthermore, the overall process efficiency depends on increasing the concentration of carbon that can be loaded into the capture solution.^[1] Scaling up the technology from laboratory proof-of-concept to industrial-scale deployment will require advances in reactor design, materials science, and integration with variable renewable energy sources.^[11][15]

The outlook for direct air electrowinning is tied to the broader push for decarbonization and the development of a circular carbon economy. If these challenges can be overcome, the technology could play a significant role in achieving net-zero emissions by providing a pathway to produce carbon-neutral fuels and chemicals directly from the air.^[9][11]

• Artificial photosynthesis
• Carbon capture and storage
• Carbon-neutral fuel
• Direct air capture
• Electrolysis of carbon dioxide
• Electrowinning
• Power-to-X