Hydroxide exchange membrane carbon capture using a nickel hydroxide symmetric battery cell

Electrochemical carbon capture devices can be a low energy cost solution for direct air capture (DAC) using renewable electricity. Historically electrochemical carbon-capture has targeted a range of concentrations from atmospheric (400 ppm _CO2 ) (DAC), ¹ to life-support (5000 ppm _CO2 ), ² to point-source capture (10% CO ₂ ). ³ The hydroxide exchange membrane nickel hydroxide symmetric battery cell with two identical electrodes has low voltage requirements making it more suitable for DAC than other electrochemical approaches. A 25 cm ² laboratory cell shows an average energy cost of 1.15 MWh·ton _CO2 ⁻¹ and a CO ₂ flux of 78 kg _CO2 ·m ² ·yr ^− 1 at 2 mA·cm ^− 2 . A manufacturable 25 cm ² cell is durability tested for 5000 hours and achieves an energy of 0.46 MWh·ton _CO2 ⁻¹ and a flux of 62 kg _CO2 ·m ² ·yr ^− 1 at the end of the test. A DAC pilot system with a stack of 9 scaled-up 300 cm ² cells demonstrates an energy of 0.83 MWh·ton _CO2 ⁻¹ and a flux of 75 kg _CO2 ·m ² ·yr ^− 1 and meets the 300 Pa pressure drop required for DAC. ⁴ Modular design projects improvements in cost from manufacturing and economies of scale, and a pathway to below 100 $·ton _CO2 ⁻¹ from learning rates of past energy technologies. ⁵