A high-purity gas–solid photoreactor for reliable and reproducible photocatalytic CO₂ reduction measurements

Reactions between a gas phase and a solid material are of high importance in the study of alternative ways for energy conversion utilizing otherwise useless carbon dioxide (CO₂). The photocatalytic CO₂ reduction to hydrocarbon fuels like e.g., methane (CH₄) is such a potential candidate process converting solar light into molecular bonds. In this work, the design, construction, and operation of a high-purity gas–solid photoreactor is described. The design aims at eliminating any unwanted carbon-containing impurities and leak points, ensuring the collection of reliable and reproducible data in photocatalytic CO₂ reduction measurements. Apart from the hardware design, a detailed experimental procedure including gas analysis is presented, allowing newcomers in the field of gas–solid CO₂ reduction to learn the essential basics and valuable tricks. By performing extensive blank measurements (with/without sample and/or light) the true performance of photocatalytic materials can be monitored, leading to the identification of trends and the proposal of possible mechanisms in CO₂ photoreduction. The reproducibility of measurements between different versions of the here presented reactor on the ppm level is evidenced.