A Light-Permeable Solar Evaporator with Three-Dimensional Photocatalytic Sites to Boost Volatile-Organic-Compound Rejection for Water Purification

Abstract

Solar-driven interfacial evaporation (SIE) is emerging as an energy-efficient technology to alleviate the global water shortages. However, there is a fatal disadvantage in using SIE, that is, the volatile organic compounds (VOCs) widely present in feedwater would concurrently evaporate and transport in distilled water, which threatens the water safety. Photocatalysis is a sustainable technology for pollution control, and after years of development, it has become a mature method. Considering the restriction by the insufficient reaction of the permeating VOCs on the two-dimensional (2D) light-available interface of conventional materials, a 3D photocatalytic approach can be established to boost VOC rejection for photothermal evaporation. In the present work, a light-permeable solar evaporator with 3D photocatalytic sites is constructed by a porous sponge decorated with BiOBrI nanosheets with oxygen-rich vacancies. The 3D microchannels in the evaporator provide a light-permeable path with the deepest irradiation depth of about 580 μm, and the reactive interface is increased by tens of times compared with the traditional 2D membrane, resulting in suppression of VOC remnants in distilled water by around four orders of magnitude. When evaporating river water containing 5 mg L^-1 extra added phenol, no phenol residues (below 0.001 mg/L) were detected in the produced freshwater. This development is believed to provide a powerful strategy to resolve the VOC bottleneck of SIE.