Two Birds One Stone: Facile and Controllable Synthesis of the Ag Quantum Dots/Reduced Graphene Oxide Composite with Significantly Improved Solar Evaporation Efficiency and Bactericidal Performance

A lignin-derived carbon dot-upgraded bacterial cellulose membrane as an all-in-one interfacial evaporator for solar-driven water purification

Solar-driven interfacial evaporation has emerged as an efficient approach for wastewater treatment and seawater desalination. New trends demand adaptive technology to develop photothermal membranes with multifunctional features. Herein, we report a robust multi-purpose near-infrared (NIR)-active hydrogel composite (c-BC@N-LCD) from broad-spectrum active nitrogen-doped lignin-derived carbon dots (N-LCDs) covalently cross-linked with a bacterial cellulose (BC) matrix. BC provides adequate porosity and hydrophilicity required for easy water transport while managing heat loss. A commendable evaporation rate (ER) of 2.2 kg m-2 h-1 under one sun (1 kW m-2) is achieved by c-BC@N-LCD. The developed hydrogel system is also found to be efficient for desalination (∼2.1 kg m-2 h-1) and for remediating various pollutants (heavy metal ions, dyes, and pharmaceuticals) from feed water. The efficacy of the membrane remains unaltered by different grades of water, and hence can be adoptable for economically stressed communities living in water-polluted regions as well as those residing in coastal areas.

Enhancing Solar-Driven Water Purification by Multiscale Biomimetic Evaporators Featuring Lamellar MoS2/GO Heterojunctions

Solar-powered steam generation holds a strong sustainability in facing the global water crisis, while the production efficiency and antifouling performance remain challenges. Inspired by river moss, a multiscale biomimetic evaporator is designed, where the key photothermal conversion film composed of lamellar MoS2/graphene oxides (GO) can significantly enhance the evaporation efficiency and solve the problem of fouling. First-level leaf-like MoS2/GO nanosheets, obtained by a modified hydrothermal synthesis with an assisted magnetic-field rotation stirring, are self-assembled into a second-level nanoporous film, which achieves an evaporation rate (ER) of 1.69 kg m-2 h-1 under 1 sun illumination and an excellent self-cleaning ability. The tertiary-bionic evaporator with a macroscopic crownlike shape further enhances the ER to 3.20 kg m-2 h-1, 189% above that of planar film, yielding 20.25 kg m2 of freshwater from seawater during a daytime exposure of 6 h. The exceptional outcomes originate from the macroscopic biomimetic design and the microscopic integration of heterojunction interfaces between the MoS2 and GO interlayers and the nanoporous surface. The biomimetic evaporator indicates a potential direction through surface/interface regulation of photothermal nanomaterials for water desalination.

A scalable and anti-fouling silver-nickel/cellulose paper with synergy photothermal effect for efficient solar distillation

Solar interfacial evaporation is one of the most efficient and environmentally-friendly clean freshwater production technologies. Plasma metal nanoparticles are excellent optical absorption materials, but their high cost and inherent resonance narrow bandwidth absorption limit their application. In this work, commercial cellulose papers are used as substrates to synthesize Ag-Ni/cellulose paper by the seed-mediated method. The Ag-Ni/cellulose paper exhibits high light absorption at the full wavelength (200-2500 nm) resulting from the synergistic effect of localized surface plasmon resonance (LSPR) of Ag NPs and the interband transitions (IBTs) of Ni. Under one-sun irradiation (1 kW m-2), the energy utilization efficiency of Ag-Ni/cellulose paper is as high as 93.8%, and the water evaporation rate is 1.87 kg m-2 h-1. Diffusion inhibition experiment results show that the Ag-Ni/cellulose paper exhibits excellent antibacterial performance, and the antibacterial performance is highly related with Ag NPs content. These provide new opportunities for commercial production of competitive cost, green, and portable solar evaporators for different application sceneries.

High-performance solar-driven interfacial evaporation through molecular design of antibacterial, biomass-derived hydrogels

Hydrogel has been regarded as one of the most promising candidates for next-generation solar evaporation technology to produce freshwater from non-potable water. However, synthesizing hydrogel absorbers that can precisely regulate water state and significantly reduce the water vaporization enthalpy remains a grand challenge. Herein, we report the rational design of a novel hydrogel hybrid solar evaporator constructed by poly(vinyl alcohol) and sodium lignosulfonate (SLS), with addition of carbon nanotube as a light absorption material. The abundant sulfonate and hydroxyl groups of SLS enhance the interplay between hydrogel and water molecule through electrostatic interaction and hydrogen bond. As such, the presence of SLS not only remarkably promotes the hydrophilicity and water transport of hydrogel, but also precisely tunes the state of water molecule and the content of intermediate water for reducing the water vaporization enthalpy. The combined advantageous features endow the as-prepared hydrogel with an evaporation rate up to 2.09 kg m^-2 h^-1 under 1 Sun illumination, along with good anti-acid/basic abilities, antibacterial property, high salt-tolerance, and self-cleaning capability in purifying different types of wastewater. Finally, an outdoor solar seawater desalination device is designed to generate drinking water from seawater. The daily drinking water production amount per square meter is ca. 13 kg, which satifies the five adults' daily water consumption (12.5 kg). The present study highlights that rationally constructing the molecular architecture of hydrogel and tuning the interplay between water and hydrogel are effective strategies to fabricate advanced hydrogel solar evaporators for addressing the global freshwater shortage.