Renyuan Li

Hydrophobic Light‐to‐Heat Conversion Membranes with Self‐Healing Ability for Interfacial Solar Heating

Self-healing hydrophobic light-to-heat conversion membranes for interfacial solar heating are fabricated by deposition of light-to-heat conversion material of polypyrrole onto a porous stainless-steel mesh, followed by hydrophobic fluoroalkylsilane modification. The mesh-based membranes spontaneously stay at the water-air interface, collect and convert solar light into heat, and locally heat only the water surface for enhanced evaporation.

MXene Ti3C2: An Effective 2D Light-to-Heat Conversion Material

MXene, a new series of 2D material, has been steadily advancing its applications to a variety of fields, such as catalysis, supercapacitor, molecular separation, electromagnetic wave interference shielding. This work reports a carefully designed aqueous droplet light heating system along with a thorough mathematical procedure, which combined leads to a precise determination of internal light-to-heat conversion efficiency of a variety of nanomaterials. The internal light-to-heat conversion efficiency of MXene, more specifically Ti3C2, was measured to be 100%, indicating a perfect energy conversion. Furthermore, a self-floating MXene thin membrane was prepared by simple vacuum filtration and the membrane, in the presence of a rationally chosen heat barrier, produced a light-to-water-evaporation efficiency of 84% under one sun irradiation, which is among the state of art energy efficiency for similar photothermal evaporation system. The outstanding internal light-to-heat conversion efficiency and great light-to-water evaporation efficiency reported in this work suggest that MXene is a very promising light-to-heat conversion material and thus deserves more research attention toward practical applications.

Dual-template engineering of triple-layered nanoarray electrode of metal chalcogenides sandwiched with hydrogen-substituted graphdiyne

Hybrid nanostructures integrating electroactive materials with functional species, such as metal-organic frameworks, covalent organic frameworks, graphdiyne etc., are of significance for both fundamental research and energy conversion/storage applications. Here, hierarchical triple-layered nanotube arrays, which consist of hydrogen-substituted graphdiyne frameworks seamlessly sandwiched between an outer layer of nickel–cobalt co-doped molybdenum disulfide nanosheets and an inner layer of mixed cobalt sulfide and nickel sulfide (Co9S8/Ni3S2), are directly fabricated on conductive carbon paper. The elaborate triple-layered structure emerges as a useful hybrid electrode for energy conversion and storage, in which the organic hydrogen-substituted graphdiyne middle layer, with an extended π-conjugated system between the electroactive nanomaterials, provides built-in electron and ion channels that are crucial for performance enhancement. This dual-template synthetic method, which makes use of microporous organic networks to confine a self-template, is shown to be versatile and thus provides a promising platform for advanced nanostructure-engineering of hierarchical multi-layered nanostructures towards a wide range of electrochemical applications.Multi-shelled nanomaterials offer interesting electrochemical properties, but have been limited in composition. Here the authors use dual templating to integrate electroactive metal chalcogenide layers with hydrogen-substituted graphdiyne, achieving electrocatalytic activity for hydrogen evolution.

A Hybrid Hydrogel with High Water Vapor Harvesting Capacity for Deployable Solar-Driven Atmospheric Water Generator

The Earths atmosphere holds approximately 12u202f900 billion tons of fresh water distributed all over the world with fast replenishment. Atmospheric water harvesting is emerging as a promising strategy for clean water production in arid regions, land-locked areas, and remote communities. The water vapor sorbent is the key component for atmospheric water harvesting devices based on absorbing-releasing process. In this work, a flexible hybrid photothermal water sorbent composed of deliquescent salt and hydrogel was rationally fabricated. It possesses superior water sorption capacity even in low humidity air thanks to the deliquescent salt and maintains a solid form after it sorbs a large amount of water owing to the hydrogel platform. The harvested water could be easily released under regular sunlight via the photothermal effect, and it can be directly reused without noticeable capacity fading. An easy-to-assemble-at-household prototype device with 35 g of the dry hydrogel was tested outdoors under field conditions and delivered 20 g of fresh water within 2.5 h under natural sunlight. It is estimated that the material cost of making such a device to supply minimum daily water consumption for an adult (i.e., 3 kg) is only

Harvesting Water from Air: Using Anhydrous Salt with Sunlight

3.20 (USD). This type of atmospheric water generator (AWG) is cheap and affordable, works perfectly with a broad range of humidity, does not need any electricity, and thus is especially suitable for clean water production in remote areas.

Solar Evaporator with Controlled Salt Precipitation for Zero Liquid Discharge Desalination

Atmospheric water is an abundant alternative water resource, equivalent to 6 times the water in all rivers on Earth. This work screens 14 common anhydrous and hydrated salt couples in terms of their physical and chemical stability, water vapor harvesting, and release capacity under relevant application scenarios. Among the salts screened, copper chloride (CuCl2), copper sulfate (CuSO4), and magnesium sulfate (MgSO4) distinguish themselves and are further made into bilayer water collection devices, with the top layer being the photothermal layer, while the bottom layer acts as a salt-loaded fibrous membrane. The water collection devices are capable of capturing water vapor out of the air with low relative humidity (down to 15%) and releasing water under regular and even weakened sunlight (i.e., 0.7 kW/m2). The work shines light on the potential use of anhydrous salt toward producing drinking water in water scarce regions.

Nature-Inspired, 3D Origami Solar Steam Generator toward Near Full Utilization of Solar Energy

A sustainable supply of clean water is essential for the development of modern society, which has become increasingly dependent on desalination technology since 96.5% of the water on Earth is salt water. Thousands of desalination plants are producing massive waste brine as byproduct, and the direct discharge of brine raises serious concerns about its ecological impact. The concept of zero liquid discharge (ZLD) desalination is regarded as the solution, but the current ZLD technologies are hampered by their intensive use of energy and high cost. In this work, a 3D cup shaped solar evaporator was fabricated to achieve ZLD desalination with high energy efficiency via solar distillation. It produces solid salt as the only byproduct and uses sunlight as the only energy source. By rationally separating the light absorbing surface from the salt precipitation surface, the light absorption of the 3D solar evaporator is no longer affected by the salt crust layer as in conventional 2D solar evaporators. Therefore, it can be operated at an extremely high salt concentration of 25 wt % without noticeable water evaporation rate decay in at least 120 h. This new solar evaporator design concept offers a promising technology especially for high salinity brine treatment in desalination plants to achieve greener ZLD desalination as well as for hypersaline industrial wastewater treatment.

Spectrally Selective Smart Window with High Near-Infrared Light Shielding and Controllable Visible Light Transmittance

Solar steam generation, due to its capability of producing clean water directly by solar energy, is emerging as a promising eco-friendly and energy-efficient technology to address global challenges of water crisis and energy shortage. Although diverse materials and architectures have been explored to improve solar energy utilization, high efficiency in solar steam generation could be accomplished only with external optical and thermal management. For the first time, we report a deployable, three-dimensional (3D) origami-based solar steam generator capable of near full utilization of solar energy. This auxetic platform is designed based on Miura-ori tessellation and is able to efficiently recover radiative and convective heat loss as well as to trap solar energy via its periodic concavity pattern. The 3D solar steam generator device with a nanocarbon composite of graphene oxide and carbon nanotubes being photothermal component in this work shows a very strong dependence between its solar energy efficiency and surface areal density. The device yields an extraordinary solar energy efficiency close to 100% under 1 sun illumination at a highly folded configuration. The 3D origami device can withstand a great number of folding and unfolding cycles and shows unimpaired solar steam generation performances. The unique structural feature of the 3D origami structure offers a new insight into the future development of highly efficient and easily deployable solar steam generator.

Rational design of nanomaterials for water treatment

Smart windows with high near-infrared (NIR) light shielding and controllable visible light transmittance are highly sought after for cooling energy saving in buildings. Herein, we present a rationally designed spectrally selective smart window which is capable of shielding 96.2% of the NIR irradiation from 800 to 2500 nm and at the same time permitting acceptable visible light (78.2% before and 45.3% after its optical switching) for indoor daylighting. The smart window synergistically integrates the highly selective and effective NIR absorption based photothermal conversion of cesium tungsten bronze (Cs xWO3) with the transparent thermoresponsive poly( N-isopropyl acrylamide) (PNIPAM) microgel-polyacrylamide (PAM) hydrogel. Optical switching of the smart window is a direct result of the phase transition of PAM-PNIPAM hydrogel, which in turn is induced by the photothermal effect of Cs xWO3 under sunlight irradiation. The smart window exhibits fast optical switching, shows long-term operational stability, and can be made highly flexible. Under the experimental conditions in this work, the indoor temperature with the smart window is ∼21 °C lower than that with a regular single-layered glass window under one sun irradiation. The smart window design in this work is meaningful for further development of effective smart windows for energy saving in the build environment.