Hierarchical cactus-like microsphere network membranes engineered via multiple polyphenol-mediated complexation for efficient solar-powered water purification

Abstract

The emerging solar steam generation technology enables an alternative water purification strategy, which shows great potential for alleviating the global energy and water crisis. The elaborate designs of interfacial photothermal materials play important roles in promoting solar steam generation. Herein, novel photothermal membranes with tailored hierarchical cactus-like microsphere networks are fabricated via multiple polyphenol-mediated complexation. The hierarchical cactus-like microsphere network exhibits bi-continuous, superwetting and photothermal functional features, which play critical roles in balancing solar-to-thermal and water-to-steam conversion. The tightly distributed hierarchical cactus-like microspheres simultaneously trap sunlight inside the porous network, and thus promote localized solar-to-thermal conversion. The bi-continuous porous and superhydrophilic microsphere network provides efficient water-transport/vapor-escape channels and facilitates water-to-steam conversion. These features endow the photothermal membrane with a high evaporation rate of 1.83 kg m⁻² h⁻¹ and a solar-to-vapor conversion efficiency of 95.2% under one sun illumination. The photothermal membranes are also demonstrated to produce clean water by seawater desalination and wastewater decolorization. Moreover, the universality of the proposed strategy to engineer hierarchical cactus-like microsphere network membranes provides a scalable and flexible platform for promising solar-powered water purification application.