Polymeric carbon nitrides (PCN) are sustainable, tunable, non-toxic and chemically stable materials, that have been utilized in the construction of various photocatalytic systems for a wide range of light-driven reactions, including hydrogen evolution, water oxidation, CO2 reduction, organic pollutant degradation, or selective chemical conversions . Notably, a vast majority of the studies on PCN-based photocatalytic systems encompassed investigations of suspensions of PCN powders, whereas studies of photoelectrocatalytic systems utilizing PCN-based photoelectrodes are much less frequent. In this context, it is important to realize thatapart from some drawbacks (e.g., increased installation costs due to photoelectrode and reactor fabrication)there are several advantages associated with carrying out photoelectrocatalytic reactions in well-designed photoelectrochemical cells. From a technological point of view, it is preferable to have the products of the oxidation and reduction reactions separated in the two compartments of the photoelectrochemical cell. Furthermore, the (photo)anodic and (photo)cathodic half-cells can be first optimized separately, to beeventuallyimplemented into a tandem photoelectrochemical device. Finally, from a more fundamental and scientific point of view, photoelectrocatalytic cells allow for studying light-driven conversions also in the absence of any additional (sacrificial) oxidizing and reducing agents which are typically used in photocatalytic studies using suspensions. Indeed, it is one of the many significant scientific contributions of Professor Detlef Bahnemann that he has repeatedly pointed out how the activity of many photocatalytic systems is often dictated by the reactivity of the sacrificial reagents, rather than by the intrinsic charge-separation dynamics and kinetics of photocatalyzed redox reactions under investigation . Studies of truly photoelectrocatalytic systems without any additional reducing and oxidizing agents are therefore of paramount importance.