Making Photocatalysis Comparable Using a Modular and Characterized Open‐Source Photoreactor**

Abstract

Reproducibility and comparability of photocatalytic experiments are still challenging, owing to the large number of experimental parameters and their comprehensive documentation. To overcome this limitation, a modular, adaptable, and extensible photoreactor platform is reported, which enables experiments under well‐characterized, reproducible conditions. Comparability is ensured by comprehensive photonic characterization with chemical actinometry, radiometry and open documentation of the incident photon fluxes in the reaction vessels for different setups as well as the homogeneity of irradiation in multi‐reactor setups. Comprehensive documentation minimizes the need for repeated photonic characterization when modifying the setups. Experimental reproducibility within and across experiments was evaluated with studies of photocatalytic systems for hydrogen evolution, emphasizing the validity of the concept.