Electrochemical DAC promises up to 50 per cent energy gains

Direct air capture (DAC) – where CO2 is pulled directly from the atmosphere – is viewed as an essential tool to mitigate the worst effects of the climate crisis. Existing methods generally use heat to release chemically captured CO2, but this process requires significant energy, which in turn poses economic challenges for the technology. 

Developed at Rice University, the new DAC technique uses a single-step electrochemical processes to separate CO2 from carbonate and bicarbonate solutions (NaHCO₃/Na₂CO₃). Rice engineers used a modular porous solid electrolyte (PSE) reactor to harvest the CO2, generating an alkaline absorbent (NaOH ). The work is published in Nature Energy.

“Our research findings present an opportunity to make carbon capture more cost-effective and practically viable across a wide range of industries,” said corresponding author Haotian Wang, Associate Professor of Chemical and Biomolecular Engineering at Rice.

“Our reactor can efficiently split carbonate and bicarbonate solutions, producing alkaline absorbent in one chamber and high-purity carbon dioxide in a separate chamber. Our innovative approach optimises electrical inputs to efficiently control ion movement and mass transfer, reducing energy barriers.”

According to the Rice team, the reactor has already achieved ‘industrially relevant’ rates of carbon dioxide regeneration from carbonous solutions. They believe its performance metrics, including its long-term stability and adaptability to different cathode and anode reactions, showcase its potential for wide-scale industrial use. What’s more, the electrochemical process could be paired with different inputs to cogenerate hydrogen, according to Wang. 

“One of the major draws of this technology is its flexibility,” he said. “Hydrogen coproduction during direct air capture could translate into dramatically lower capital and operation costs for downstream manufacturing of net-zero fuels or chemicals.”

Other authors on the study include study co-author Zhiwei Fang, former Rice postdoctoral researcher Xiao Zhang, and doctoral alumni and former postdoctoral scientists Peng Zhu and Yang Xia.