Gradient-structured directional porous floatable aerogels for effective solar-driven hydrogen production and steam generation.

Solar-driven reaction technology offers a promising route to clean energy generation and sustainable development. Despite significant advancements in photocatalysts and photothermal materials, challenges remain in device structural design, including insufficient light utilization, slow water transport, and inefficient gas separation. Here, we design a floatable cellulose nanofiber aerogel featuring a gradient-structured directional porous architecture to address these challenges. The designed aerogel integrates multiple structural features, including a bottom layer with large directional channels for rapid water transport, a top functional floatable layer with small directional channels for enhanced gas separation and active material loading, and a micron-scale embossed surface structure to maximize light utilization. As a result, the photocatalytic aerogels achieved a high hydrogen generation rate of 60.7 mmol m h, significantly outperforming the conventional thin-film photocatalytic platforms. Meanwhile, the photothermal aerogels exhibited a high water evaporation rate of 1.62 kg m h with excellent salt-resistance capability, and a high freshwater collection rate of 1.65 mL m h under outdoor field-scale conditions. This study demonstrates a novel and scalable strategy for developing high-efficiency solar-driven reaction platforms, with strong potential for future industrial applications.