Temperature-gated active salt secretion enables stable photothermal evaporation

Abstract

Photothermal evaporation offers a sustainable solution for brine and seawater desalination, yet its long-term operation is fundamentally limited by salt accumulation arising from diffusion-limited ion transport, especially under high evaporative flux. Here, inspired by the active salt secretion of the mangrove, we develop a temperature-responsive evaporator that actively regulates ion transport through temperature-gated channel dynamics for stable high-flux evaporation. By integrating thermoresponsive poly(N-isopropylacrylamide) within an ordered reduced graphene oxide-carbon nanotube architecture, the system achieves reversible contraction and swelling with a ratio of 87%, enabling continuous water replenishment during heating and efficient expulsion of concentrated brine upon cooling. This salt secretion process accelerates salt backflow by over 2 orders of magnitude compared with conventional diffusion-driven transport, effectively renewing the evaporation surface and sustaining stable high-flux water collection (∼3.40 kg m−2 h−1) under diverse saline conditions and solar intensities. By replacing passive structural optimization with active transport regulation, this work establishes a new strategy for salt management in photothermal desalination and adaptive interfacial transport systems.