Enhanced hydrogen peroxide photosynthesis via charge-complementary π-electron sites
Yan Guo, Qixin Zhou, Li Wang, Ziqi Deng, David Lee Phillips, Chuyang Y. Tang, Yongfa Zhu
Abstract
Organic photocatalysts with porphyrin conjugated chromophore core are promising for artificial hydrogen peroxide (H2O2) photosynthesis, but the lack of bottom-up paradigm for oxygen (O2) adsorption sites hinders their activity. Here, we introduce imidazole groups as π-electron sites with charge-complementarity to the O2 molecules, enhancing O2 binding via sub-atomically mirrored electrostatic cooperative π-π dispersion forces. In situ spectroscopy and theory reveal that the ~2 Å linear δ+-δ−-δ+ domain of the imidazole substituent exhibits 2.8-folds stronger O2 adsorption than neutral π-electron substituents, accompanied by the generation of energetically peroxide intermediates. Consequently, imidazole-substituted porphyrin photocatalysts achieve a solar-to-chemical conversion efficiency of 1.85% using only H2O and O2. In scalable membranes with photocatalysts, enabling daily photosynthetic production of 80 L m−2 of Fenton-applicable H2O2 solution. This work offers a strategy to modulate the electrostatic distribution of oxygen photoreduction sites, providing insights into overcoming gas activation rate-limiting steps in photocatalytic processes. Introducing imidazole groups into porphyrin structures creates charge-complementary π-electron sites for O2 molecules which enhances binding force via electrostatic cooperative dispersion, thereby improving the efficiency of H2O2 photosynthesis.