Diverse catalytic behavior of a dye-based polymer metal-free catalyst for hydrogen peroxide photoproduction

Metal-free polymer-based catalysts have shown promising photocatalytic performance for efficient hydrogen peroxide (H2O2) photoproduction under visible light. However, the structure of the active site and the interface charge transfer of these catalysts have not been revealed clearly. Here, we report the fabrication of four narrow bandgap single-dye-based polymer metal-free catalysts (PPC-X, X = 75, 100, 125, 175). The catalyst PPC-X was synthesized by a hydrothermal method using proanthocyanidin (OPC) as the raw material. The reaction temperature was set at 75 °C, 100 °C, 125 °C, and 175 °C, and finally, the single-dye polymer catalyst was obtained, which was marked as PPC-X, with X representing the polymerization temperature. The PPC-X as catalysts show diverse catalytic behavior for H2O2 photoproduction. Under visible light excitation, the PPC-X catalysts (X = 100, 125, 175) reduced O2 to produce H2O2via the two-electron transfer pathway and oxidized water to release O2 by the four-electron transfer pathway. For the PPC-75 catalyst, O2 was reduced by photo-generated electrons on the catalyst surface via the two-electron transfer pathway, while the PPC-75 catalyst itself also serves as a sacrificial agent to consume the photo-generated holes, leading to a high H2O2 production. The H2O2 yield of PPC-75 is 1152 μmol g−1 h−1, and that of PPC-100 is up to 1214 μmol g−1 h−1 at a light intensity of 32.6 mW cm−2. This work provides a practical research example and idea for the in-depth understanding and design of efficient polymer-based photocatalysts.