Arch-Bridge Evaporator Constructed from the Natural Collagen Fiber Network for Efficient Solar Desalination

Abstract

Solar-driven interfacial evaporation has gained increasing attention as an eco-friendly and energy-efficient approach for seawater desalination and wastewater purification. However, its practical deployment remains constrained by insufficient broadband solar absorption, unavoidable thermal dissipation, and salt crystallization at the evaporation interface. Herein, inspired by architectural arch-bridge structures, we report a three-dimensional (3D) arch-bridge-structured photothermal evaporator (PANI@CFN). It is fabricated via in-situ chemical oxidative polymerization strategy, whereby polyaniline (PANI) is uniformly deposited onto a hierarchically porous collagen fiber network (CFN). The 3D arch-bridge architecture enhances optical trapping and promotes interfacial thermal localization, while the intrinsic nano/microchannel structure of CFN enables rapid and continuous water transport through capillary pumping. Beyond structural merits, the abundant surface polar groups (−COOH, −NH2, and −OH) on CFN serve as robust anchoring sites for PANI and facilitate interfacial hydrogen bonding with water molecules. Under nanoconfinement within the porous matrix, these functionalities disrupt bulk water hydrogen-bonding networks, enrich the intermediate water population, and effectively lower the evaporation enthalpy. Meanwhile, the interconnected 3D porous architecture ensures rapid capillary-driven water replenishment that continuously dilutes the interfacial brine while laterally conveying excess salt toward the edges of the arch-bridge, where preferential crystallization occurs away from the primary photothermal interface. Benefiting from the synergistic integration of broadband photothermal conversion, localized thermal management, capillary-driven water/salt transport, and interfacial water-state modulation, PANI@CFN achieves a high evaporation rate of 2.70 kg m–2 h–1 under one-sun irradiation. Notably, it maintains a comparable rate of 2.69 kg m–2 h–1 in 3.5 wt % NaCl solution. Outdoor evaporation tests further demonstrate a freshwater yield of 11.13 kg m–2 over 10 h. This work advances the structural and interfacial engineering of biomass-derived photothermal evaporators, presenting a scalable strategy for sustainable solar-driven water purification.