Nonmetallic Abiotic-Biological Hybrid Photocatalyst for Visible Water Splitting and Carbon Dioxide Reduction

Both artificial photosystems and natural photosynthesis have not reached their full potential for the sustainable conversion of solar energy into specific chemicals. A promising approach is hybrid photosynthesis combining efficient, non-toxic, and low-cost abiotic photocatalysts capable of water splitting with metabolically versatile non-photosynthetic microbes. Here, we report the development of a water-splitting enzymatic photocatalyst made of graphitic carbon nitride (g-C₃N₄) coupled with H₂O₂-degrading catalase and its utilization for hybrid photosynthesis with the non-photosynthetic bacterium Ralstonia eutropha for bioplastic production. The g-C₃N₄-catalase system has an excellent solar-to-hydrogen efficiency of 3.4% with a H₂ evolution rate up to 55.72 μmol h^-1 while evolving O₂ stoichiometrically. The hybrid photosynthesis system built with the water-spitting g-C₃N₄-catalase photocatalyst doubles the production of the bioplastic polyhydroxybutyrate by R. eutropha from CO₂ and increases it by 1.84-fold from fructose. These results illustrate how synergy between abiotic non-metallic photocatalyst, enzyme, and bacteria can augment solar-to-multicarbon chemical conversion.