H2O2 generation from O2 and H2O on a near-infrared absorbing porphyrin supramolecular photocatalyst

Photocatalytic synthesis of H2O2 is an attractive route to this important chemical and potential energy carrier, but improvements in performance and operation without sacrificial agents are needed. Here the authors report a porphyrin-based photocatalyst with promising performance for H2O2 production from only H2O and O-2. Hydrogen peroxide (H2O2) is an important industrial chemical and also a possible energy carrier. Photocatalytic synthesis of H2O2 is an attractive alternative to the anthraquinone process, but current catalyst systems suffer from many problems including: a limited sunlight wavelength response, the need for sacrificial reagents and insufficient activity. Here we report self-assembled tetrakis(4-carboxyphenyl)porphyrin supramolecular photocatalysts that produce H2O2 from only H2O and O-2 and with a quantum efficiency of 14.9% at 420 nm and 1.1% at 940 nm. The catalyst achieves a solar-to-chemical conversion efficiency of 1.2% at 328 K when irradiated and heated with simulated sunlight. Our results suggest that photogenerated electrons and holes contribute to H2O2 production by reacting on different active sites including pyrrole N-H ring and carboxyl groups. In particular, we propose a hole-induced H2O2 production process, which involves the photoconversion of -COOH to -CO3H groups on the catalyst, followed by thermal decomposition.