A scalable integrated solar device for the autonomous production of green methane

The solar-driven conversion of CO₂ into molecules with high calorific value is a major challenge to reduce the carbon footprint of industrialized countries. Many concepts are proposed, but limited action has been undertaken so far to design, integrate, and scale commercially viable technologies. Here, we report on the long-term performance of an autonomous solar-driven device that continuously converts CO₂ into CH₄ under mild conditions. It couples a biomethanation reactor to a set of integrated photoelectrochemical cells, combining silicon/perovskite tandem solar cells with proton exchange membrane electrolyzers, for the production of solar hydrogen from water. The 5.5% solar-to-fuel yield (calculated from global horizontal irradiance) achieved by the bench-scale device during 72 h of outdoor operation at JRC, Ispra, Italy, in July 2022, demonstrates that re-design and close integration of proven lab-scale concepts can overcome the technological barriers to the industrial deployment of artificial photosynthesis process.