Development of a Reactor for Standardized Quantification of the Photocatalytic Hydrogen Production The photocatalytic splitting of water is considered as a dream reaction for a sustainable hydrogen production. In combination with fuel cells it could be the future green power generation. In order to identify suitable catalyst materials the half reactions have to be studied individually under conditions as close as possible to reality. In this contribution an experimental setup for the quantitative determination of the performance of photocatalysts is introduced and tested with mesoporous carbon nitride, a promising catalyst material. The obtained hydrogen production rate is used for a comparison with photovoltaic and water electrolysis and also for the design of a prototype reactor.