Natural Cellulose Fiber-Derived Photothermal Aerogel for Efficient and Sustainable Solar Desalination.

Aerogels are becoming a promising platform to fabricate photothermal materials for use in solar steam generation (SSG), which have remarkable application potential in solar desalination, due to their excellent thermal management, salt resistance, and considerable water evaporation rate. In this work, a novel photothermal material is fabricated by forming a suspension between sugarcane bagasse fibers (SBF) and poly(vinyl alcohol), tannic acid (TA), and Fe3+ solutions via hydrogen bonds of hydroxyl groups. After freeze drying, the fabricated SBF aerogel-based photothermal (SBFAP) material possesses a 3D interconnected porous microstructure, which could enhance water transportation ability, reduce thermal conductivity, and quickly dissolve salt crystals on the SBFAP surface. Thanks to the formation of micro/nanosized complexes between TA and Fe3+ ions on the SBFAP material, the SBFAP exhibits high light capture and water evaporation rate (2.28 kg m-2 h-1). In particular, due to strong hydrogen bonding and the SBF, the SBFAP material is reinforced, thereby exhibiting excellent structural stability in seawater. Moreover, the high salt tolerance of SBFAP favors its high desalination performance for at least 76 days of continuous evaporation under actual conditions. This research paves the way for the fabrication of natural cellulose fiber-based photothermal materials for application in solar desalination.

Flexible, affordable and environmentally sustainable solar vapor generation based on ferric tannate/bacterial cellulose composite for efficient desalination solutions.

Desalination by solar steam generation (SSG) system is a green technology to produce pure water, which can address the issue of water scarcity. A novel photothermal material for the SSG system was fabricated by immersing bacterial cellulose (BC) sequentially into tannic acid (TA) and iron(iii) (Fe3+) solutions. Surface analysis of the resulting BC-TA-Fe3+ (BTF) material showed that coordination nanocomplexes between Fe3+ and hydroxyl groups of TA were formed on the surface of cellulose nanofibers. BTF material exhibited high sunlight absorption (∼95%), hydrophilic, self-cleaning properties, and excellent structural stability. SSG systems based on BTF had an evaporation efficiency of 91% and an evaporation rate of 1.56 kg m-2 h-1 under 1 sun illumination. Then, an efficient desalination device based on the larger-scale BTF material was fabricated to produce freshwater, the amount of freshwater per day was 5.6 kg m-2 on a sunny day. BTF material, thus, showed great potential in seawater desalination applications along with simple, versatile, scalable, and affordable fabrication methods.

Bio-inspired broadband absorbers induced by copper nanostructures on natural leaves.

In this work, two copper-based biometamaterials were engineered using leaves of water cabbage (Pistia stratiotes) and purple bauhinia (Phanera purpurea) as templates. The copper sputtering was implemented to produce a thin copper film on the surface of leaves. The scanning electron microscopy (SEM) images exhibited the root hair-like nanostructure of water cabbage leaf and single comb-like nanostructure of purple bauhinia leaf. In spite of copper coating, the leaf surfaces of water cabbage and purple bauhinia were black and exhibited excellent light absorption at visible and near infrarrred wavelengths. It was estimated that these two types of leaves could absorb roughly 90% of light. Finite-difference time-domain (FDTD) calculations predicted the low reflectance stemming from the leaf nanostructures and copper coating layer. Because of the low cost of copper as a coating metal and simple procedure, this can be a promising method for quick fabrication of a thin copper film on the leaf nanostructure for application in blackbody or as the light absorbers.