Proof-of-concept nanogenerator turns CO₂ into sustainable power

> "We've worked out how to make the positive ions much larger than the negative ions and because the different sizes move at different speeds, they generate a diffusion current which can be amplified into electricity to power light bulbs or any electronic device.

> "In nature and in the human body, ion transportation is the most efficient energy conversion—more efficient than electron transportation which is used in the power network."

> The two components were embedded in a hydrogel which is 90% water, cut into 4-centimeter disks and small rectangles and then tested in a sealed box pumped full of CO2.

> "When we saw electrical signals coming out, I was very excited but worried I'd made a mistake," Dr. Wang said.

"Electricity generation from carbon dioxide adsorption by spatially nanoconfined ion separation" (2024) https://www.nature.com/articles/s41467-024-47040-x :

> Abstract: Selective ion transport underpins fundamental biological processes for efficient energy conversion and signal propagation. Mimicking these ‘ionics’ in synthetic nanofluidic channels has been increasingly promising for realizing self-sustained systems by harvesting clean energy from diverse environments, such as light, moisture, salinity gradient, etc. Here, we report a spatially nanoconfined ion separation strategy that enables harvesting electricity from CO2 adsorption. This breakthrough relies on the development of Nanosheet-Agarose Hydrogel (NAH) composite-based generators, wherein the oppositely charged ions are released in water-filled hydrogel channels upon adsorbing CO2. By tuning the ion size and ion-channel interactions, the released cations at the hundred-nanometer scale are spatially confined within the hydrogel network, while ångström-scale anions pass through unhindered. This leads to near-perfect anion/cation separation across the generator with a selectivity (D-/D+) of up to 1.8 × 106, allowing conversion into external electricity. With amplification by connecting multiple as-designed generators, the ion separation-induced electricity reaching 5 V is used to power electronic devices. This study introduces an effective spatial nanoconfinement strategy for widely demanded high-precision ion separation, encouraging a carbon-negative technique with simultaneous CO2 adsorption and energy generation.