Solar Air-to-Fuel Technologies for a Circular Carbon Economy

The CO₂ present in our atmosphere is a universally available and abundant carbon feedstock, but it exists only in dilute concentrations (currently around 427 ppm). Clean technologies capable of capturing atmospheric CO₂ using direct air capture and directly converting it into synthetic fuels and chemicals using solar energy could pave the way for a circular chemical industry. Challenges in developing such a solar-powered air-to-fuel technology that mimics photosynthesis include the use of the low CO₂ concentration in air, the thermodynamic stability of CO₂ (and its capture products), the high O₂ content (21%) in air (which often interferes with catalytic CO₂ valorization), and the presence of variable moisture levels. This perspective explores different concepts and emerging technologies for the solar-powered conversion of atmospheric CO₂ into fuels and chemicals, examines their scientific principles, considers their scalability, and offers recommendations for future research to support the development of a net-zero circular carbon economy.