Beschreibung:
<jats:title>Abstract</jats:title><jats:p>For efficient photocatalytic hydrogen production not only the photocatalytic system itself, but also the reactor design and appropriate catalytic conditions play a central role for achieving high overall activity and long lifetimes. To investigate these points further, a fully noble‐metal‐free system for the light‐driven reduction of protons to hydrogen, consisting of a copper photosensitizer and an iron carbonyl catalyst, was chosen as a model. The traditional batch reactor was replaced by a semi‐batch photoreactor with a continuously perfused gas phase in combination with <jats:italic>in situ</jats:italic> gas chromatography. This allowed for the time resolved analysis of all gases formed and enabled a systematic investigation of the impact of different light sources, light intensities and carrier gases. The results revealed a significant change in activity due to CO removal from the catalyst caused by the continuous gas flow. This effect can be counteracted by supplying additional CO through the gas phase.</jats:p>