Researchers at the University of Cambridge (UK) have developed a reactor that can use sunlight as a power source to absorb carbon dioxide (CO2) directly from the air and convert it into sustainable fuel. The researchers said that this solar reactor can be used to make fuels to power cars and aircraft, or in the production of many chemicals and pharmaceuticals. It can also be used to produce fuels in remote or off-grid areas. The researchers said that direct air capture is an emerging energy technology that can reduce CO2 levels in the atmosphere, but the current cost of this technology is high and the consequences of long-term storage of CO2 are unclear. Another approach is to use CO2 from the atmosphere on-site to produce value-added renewable fuels, but current technologies mainly use concentrated CO2 or require high temperatures.
The Role of Solar Reactors
The researchers reported a gas-phase dual-bed direct air carbon capture and utilization flow reactor that uses light to capture CO2 from air for on-site use to produce syngas (CO+H2) without high temperature or pressure. The reactor includes a bed of solid silica amine adsorbent to capture oxygenated CO2 and produce CO2-free air; concentrated light is used to release the captured CO2 and convert it into syngas via a bed of silica/alumina-titania-cobalt bis(terpyridine) molecules-semiconductor photocatalysts.
The researchers used oxidation of depolymerized polyethylene terephthalate plastic as the reverse reaction. The technology is envisioned to operate in a diurnal manner, capturing CO2 at night and converting it into syngas during the day under concentrated sunlight.
Carbon capture and storage (CCS) is seen as a possible solution to the climate crisis. However, it is energy intensive and there are concerns about the long-term safety of burying pressurized CO2 deep underground. The latest system developed by Professor Erwin Reisner’s team absorbs CO2 directly from the air and converts it into syngas, a key intermediate in the production of many chemicals and pharmaceuticals. The researchers say this approach does not require transportation or storage and is easier to scale up than previous solar-powered devices.
The device is a solar-powered flow reactor that uses specialized filters to absorb CO2 from the air at night, like a sponge soaking up water. When the sun is out, the captured CO2 is heated by sunlight, which absorbs infrared radiation, and semiconductor powders absorb ultraviolet radiation, triggering a chemical reaction that converts the captured CO2 into solar syngas. Mirrors on the reactor focus the sunlight, making the process more efficient.
Future Research
Currently, the researchers are working to convert solar syngas into liquid fuels that can be used to power cars and airplanes, among other things. In the chemical and pharmaceutical industries, syngas can be converted into many products that people need every day without affecting the climate. The researchers are also building a larger reactor and hope to start testing it in the spring. If scaled up, the reactor could be used in a decentralized manner. In theory, this would allow individuals to produce their own fuel, which would be useful in remote or off-grid areas.
Overall, unlike most carbon capture technologies, this reactor does not require fossil fuel-based power or the transportation and storage of CO2, but instead uses sunlight to convert atmospheric CO2 into useful substances. The technology is being commercialized with support from Cambridge Enterprise, the commercialization arm of the University of Cambridge.
