Researchers propose testing standards for particulate photocatalysts in solar fuel production Utilization of renewable solar energy is crucial for addressing the global energy and environmental concerns and achieving sustainable development. In this regard, photocatalytic water splitting has attracted significant interest as a cost-effective means to convert sustainable solar energy into valuable chemicals. However, because efficiency is sensitive to reaction conditions and experimental setup, it is difficult to compare the results obtained by different research groups or provide a reliable guide for large-scale implementation. Due to the lack of testing standards, it is difficult to compare the results obtained by different research groups or provide a reliable guide for large-scale implementation.