Abstract: The invention relates to a reaction cell for the photoelectrochemical production of hydrogen gas, comprising a housing which is filled with an aqueous electrolyte, a pair of electrodes consisting of a first electrode of a doped conductor which is immersed in the electrolytes and a second electrode which is made of metal and which is immersed in the electrolytes and which is electrically conductively connected to the first electrode, also comprising a light source which illuminates the pair of electrodes. The reaction cell is characterized in that the electrodes are connected to each other in a flat manner, the pair of electrodes divides the reaction cell into two chambers, wherein the chambers are connected to each other in a fluidically conducting manner and the housing is provided with at least one gas outlet.