Multimodal Analysis of Light‐Driven Water Oxidation in Nanoporous Block Copolymer Membranes **

Heterogeneous light‐driven catalysis is a cornerstone of sustainable energy conversion. Most catalytic studies focus on bulk analyses of the hydrogen and oxygen evolved, which impede the correlation of matrix heterogeneities, molecular features, and bulk reactivity. Here, we report studies of a heterogenized catalyst/photosensitizer system using a polyoxometalate water oxidation catalyst and a model, molecular photosensitizer that were co‐immobilized within a nanoporous block copolymer membrane. Via operando scanning electrochemical microscopy (SECM), light‐induced oxygen evolution was determined using sodium peroxodisulfate (Na 2 S 2 O 8 ) as sacrificial electron acceptor. Ex situ element analyses provided spatially resolved information on the local concentration and distribution of the molecular components. Infrared attenuated total reflection (IR‐ATR) studies of the modified membranes showed no degradation of the water oxidation catalyst under the reported light‐driven conditions.