Solar Fuel Synthesis\nUsing a Semiartificial Colloidal\nZ‑Scheme

The integration of enzymes with semiconductor light absorbers\nin\nsemiartificial photosynthetic assemblies offers an emerging strategy\nfor solar fuel production. However, such colloidal biohybrid systems\nrely currently on sacrificial reagents, and semiconductor–enzyme\npowder systems that couple fuel production to water oxidation are\ntherefore needed to mimic an overall photosynthetic reaction. Here,\nwe present a Z-scheme colloidal enzyme system that produces fuel with\nelectrons sourced from water. This “closed-cycle” semiartificial\napproach utilizes particulate SrTiO<sub>3</sub>:La,Rh and BiVO<sub>4</sub>:Mo (light absorbers), hydrogenase or formate dehydrogenase\n(cocatalyst), and a molecular cobalt complex (a redox mediator). Under\nsimulated solar irradiation, this system continuously generates molecular\nhydrogen or formate, while co-producing molecular oxygen for 10 h\nusing only sunlight, water, and carbon dioxide as inputs. In-depth\nanalysis using quartz crystal microbalance, photoelectrochemical impedance\nspectroscopy, transient photocurrent spectroscopy, and intensity-modulated\nphotovoltage spectroscopy provides mechanistic understanding and characterization\nof the semiconductor–enzyme hybrid interface. This study provides\na rational platform to assemble functional semiartificial colloidal\nZ-scheme systems for solar fuel synthesis.