Vertically aligned reduced graphene oxide/Ti 3 C 2 T x MXene hybrid hydrogel for highly efficient solar steam generation
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Vertically aligned reduced graphene oxide/Ti3C2Tx MXene hybrid hydrogel for highly efficient solar steam generation Wei Li1, Xiaofeng Li1 (), Wei Chang1, Jing Wu1, Pengfei Liu1, Jianjun Wang2, Xi Yao3, and Zhong-Zhen Yu1,4 () 1
State Key Laboratory of Organic–Inorganic Composites, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China 2 Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China 3 Department of Biomedical Sciences, City University of Hong Kong, Hong Kong 999077, China 4 Beijing Key Laboratory of Advanced Functional Polymer Composites, Beijing University of Chemical Technology, Beijing 100029, China © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 22 March 2020 / Revised: 29 May 2020 / Accepted: 3 July 2020
ABSTRACT Effective utilization of abundant solar energy for desalination of seawater and purification of wastewater is one of sustainable techniques for production of clean water, helping relieve global water resource shortage. Herein, we fabricate a vertically aligned reduced graphene oxide/Ti3C2Tx MXene (A-RGO/MX) hybrid hydrogel with aligned channels as an independent solar steam generation device for highly efficient solar steam generation. The vertically aligned channels, generated by a liquid nitrogenassisted directional-freezing process, not only rapidly transport water upward to the evaporation surface for efficient solar steam generation, but also facilitate multiple reflections of solar light inside the channels for efficient solar light absorption. The deliberate slight reduction endows the RGO with plenty of polar groups, decreasing the water vaporization enthalpy effectively and hence accelerating water evaporation efficiently. The MXene sheets, infiltrated inside the A-RGO hydrogel on the basis of Marangoni effect, enhance light absorption capacity and photothermal conversion performance. As a result, the A-RGO/MX hybrid hydrogel achieves a water evaporation rate of 2.09 kg·m−2·h−1 with a high conversion efficiency of 93.5% under 1-sun irradiation. Additionally, this photothermal conversion hydrogel rapidly desalinates seawater and purifies wastewater to generate clean water with outstanding ion rejection rates of above 99% for most ions.
KEYWORDS anisotropic hydrogel, MXene, reduced graphene oxide, solar steam generation, aligned channels
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Introduction
With the rapid development of industry and the increase of ever-growing population, the shortage of clean water is becoming a global crisis. Currently, most water purification plants adopt low-temperature multi-effect distillation or reverse osmosis technology, which rely on high energy consumption and large centralized infrastructure, limiting their practical applications in offshore areas, small villages, or remote areas far from the grid. It is thus imperative to utilize sustainable and pollution-free new energy for water purification. So far, various new and unexhausted energy sources, including wind
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