Cascade Full‐Spectrum Solar Utilization on Floating Aerogels for Acetate–Freshwater Cogeneration

Ocean is a vast carbon reservoir and contains abundant solar energy resources. Using solar energy for CO 2 reduction to produce fuel while employing unused energy for seawater desalination not only maximizes solar efficiency, but also practically addresses energy and water scarcity. However, the waste of energy potential with less demanding energy‐consuming process in traditional systems has restricted the advancement of this approach. Here, we designed a floating gas diffusion photocatalyst layer achieving cascade utilization of solar energy, devoting high‐energy photons to CO 2 reduction first, while optimizing the reactants capture. Besides, the presence of a membrane made the modular light absorber recyclable. Consequently, a yield of 788.5 µmol·g −1 ·h −1 toward CH 3 COOH and 87.5% solar to vapor efficiency were achieved, marking the maximum production of C 2 product in bifunctional devices. This work provides insight into the rational design of fuel‐water co‐generators, which are practical once deployed at coastal plants.