Coupling Photocatalytic Water Oxidation and Electrocatalytic CO2 Reduction for Formate Production

Abstract Artificial photosynthesis represents a promising route for converting sunlight, water, and carbon dioxide into value-added chemicals, yet conventional systems are often limited by the sluggish kinetics and high overpotential of the oxygen evolution reaction. Inspired by the electron transport chain between PSI and PSII in natural photosynthesis, we report an artificial photosynthesis system that spatially separates solar energy capture and storage from CO2 conversion to formate using a redox mediator. In the light reaction, a facet-engineered BiVO4 photocatalyst harvests solar energy and stores photogenerated electrons in a reversible [Fe(CN)6]3–/[Fe(CN)6]4– redox mediator, achieving an apparent quantum efficiency of 23.8% in water oxidation. Facet-selective regulation of interfacial redox chemistry promotes mediator charging while suppressing reverse reactions, thereby enabling efficient water oxidation in the presence of the redox mediator. The charged mediator subsequently drives a spatially separated CO2 reduction reaction on a Bi2O3 electrocatalyst for selective formate production. This work establishes a redox-mediated artificial photosynthesis architecture that spatially and functionally decouples light-driven water oxidation from electrocatalytic CO2 reduction. Compared with conventional electrocatalytic CO2 reduction systems, the proposed strategy also reduces the cell voltage by replacing water oxidation with kinetically favorable mediator oxidation. Furthermore, such a modular design enables the independent optimization of the photocatalytic and electrocatalytic processes while providing a platform for temporal energy storage and on-demand chemical production.