Heterogeneous light-driven catalysis is a cornerstone of sustainable energy conversion schemes such as solar water splitting. However, to date most catalytic studies in the field focus on bulk analyses quantifying the amount of produced hydrogen and oxygen. Here, we report on ex situ and operando studies with micrometer to nanometer resolution of a heterogenized catalyst/photosensitizer system. As a model, the molecular photosensitizer [Ru(bpy)3]2+and the molecular metal oxide water oxidation catalyst [Co4(H2O)2(PW9O34)2]10- were co-immobilized within a nanoporous block copolymer membrane via electrostatic interactions. In a yet unprecedented approach, operandoscanning electrochemical microscopy (SECM) allowed tracking the light induced oxygen evolution with spatial and temporal resolution. Complementary ex situ element analyses using micro-X-ray fluorescence (mXRF) and scanning transmission electron microscopy/x-ray energy dispersive spectroscopy (STEM/EDX) provided spatially resolved information on the local concentration and distribution of the molecular components.