New battery-like device captures CO2 by pumping it across a stack of cells

A team at the University of Delaware led by James Buchen has demonstrated an electrochemical device that pulls carbon dioxide out of ordinary air and moves it across a battery-like stack of cells. The researchers say the method could need less energy, and therefore cost less, than the reversible-filter systems that dominate direct air capture today. The study appears in Nature Energy (DOI: 10.1038/s41560-026-02129-z).

How the cell captures CO2

Most direct air capture plants pass air through granules or a liquid that absorbs CO2, then heat that material to release the gas in a separate stream. The Delaware device instead runs the chemistry inside a cell. Hydroxide produced at the cathode reacts with CO2, turning it into carbonate or bicarbonate, which travels through the separator membrane to the anode. There the lower pH drives the reaction backwards, and the carbonate turns back into CO2 gas.

The key is that both electrodes are made of nickel hydroxide, the same material used in the cathode of older nickel-metal hydride AA and AAA batteries. Instead of storing charge for a gadget, the cell works like a chemical seesaw: apply voltage in one direction and the cathode produces hydroxide that moves to the anode; reverse the voltage and the old anode becomes the new cathode, running the same chemistry in the opposite direction. All the while, the device grabs CO2 and carries it across the cell.

Nine cells on the bench

The researchers tested a lab-scale stack of nine cells, each about the area of half a letter-sized sheet of paper. A blower pushed air through sinuous channels in the plates that sandwich every cell, using parts borrowed from fuel cells. The small rig consumed roughly 0.8 megawatt-hours of electricity per ton of captured CO2. Existing facilities that capture carbon from ambient air consume about 1.5 to 3 megawatt-hours per ton.

Cost projections

Several team members work at RepAir Carbon, a startup built on this technology, and part of the paper sketches its financial feasibility at scale. The authors estimate an initial small pilot plant would cost about $566 per ton of captured CO2. Using the learning rate from the lithium-ion battery industry and standard cost scaling for larger plants, they project that a facility with a thousand times the pilot's capacity could reach $92 per ton.

That is far below what companies such as Climeworks have achieved so far; Climeworks aims to reach $250 to $350 per ton by 2030 and has shown how hard optimistic scaling targets can be to meet. Reaching $100 per ton has long been the goal in the carbon-capture field, since costs that low could drive much wider adoption.