Directional Electron Transfer across In2S3/ZnS-Embedded Photocatalytic Membranes

Photocatalytic membranes prepared with semiconductor nanoparticles embedded in a polymer film offer a convenient approach to direct the electron and hole flow and separate reduction and oxidation products. We have now embedded In2S3 and ZnS semiconductor nanoparticles in a Nafion membrane to induce photocatalytic reactions using visible light. In addition, we incorporated a viologen redox relay within the membrane to facilitate electron transfer to thionine (TH) dissolved in water. By inserting the photocatalytic membrane in a H-cell, we can separate the oxidation and reduction products and track the electron flow using steady-state photolysis and transient absorption spectroscopy. The enhanced charge separation in the In2S3 and ZnS heterostructure at 50:50 loading allowed us to maximize the electron-transfer yield. Directing such vectorial charge transfer in a photocatalytic membrane will be useful in suppressing undesired side reactions (e.g., re-oxidation of a reduced product) and facilitating product separation.