Dual‐Asymmetric Janus Aerogel Enabled by Ambient Drying for Synergistic Hydrovoltaic and Solar Steam Generation

Abstract Hydrovoltaic electricity generator (HEG) offers a promising solution for sustainable energy harvesting from ubiquitous water sources, yet achieving simultaneously high efficiency, long‐term durability, and recyclability remains a major challenge. Here, a scalable, cost‐effective strategy is reported to construct dual‐asymmetric aerogels (DAAs) via ionic cross‐linking and ambient drying (IC‐AD) method using oppositely charged nanocelluloses and amino‐functionalized carbon nanotubes. The Janus architecture features a heterogeneous pore structure and ionizable group polarity differences across bilayer interfaces, enabling sustained water transport and directional ion migration. Compared with freeze‐dried systems, the IC‐AD method significantly enhances the aerogel's wet strength and structural integrity, facilitating stable energy output. The DAA HEG exhibits a high output voltage of 736 mV and a peak power density of 0.96 µW cm −2 , maintaining stable performance over 22 h and multiple cycles. When operated in seawater, the HEG achieves enhanced output (840 mV, 5.74 µW cm −2 ) with excellent tolerance to salinity. Beyond energy harvesting, the DAA demonstrates excellent solar steam generation (1.97 kg m −2 h −1 ) with long‐term salt resistance, enabling effective seawater desalination. This work presents an integrated aerogel platform with synergistic hydroelectric and photothermal performance, offering a promising and transformative strategy for scalable, sustainable, high‐performance energy harvesting and water treatment technologies.