Search

A comprehensive review about the state-of-the-art polymer-based radiative coolers, and our insights are outlined to advance their commercial progress.

Radiative cooling has attracted considerable attention due to its tremendous potential in exploiting the cold reservoir of deep sky. However, overcooling always occurs in the conventional static radiative coolers because they operate only in the cooling mode in both hot and cold. Therefore, a dynamic radiative cooler based on phase change materials is highly desired. Nevertheless, the practical outdoor phase-change-based dynamic radiative cooling has not yet been experimentally demonstrated. To satisfy the stringent requirement of the phase-change-based radiative cooler in outdoor weather conditions, we engineered the phase-change material (VO

The electrochemical CO2 reduction (ECR) to produce value-added fuels and chemicals using clean energy sources (like solar and wind) is a promising technology to neutralize the carbon cycle and reproduce the fuels. Presently, the ECR has been the most attractive route to produce carbon-building blocks that have growing global production and high market demand. The electrochemical CO2 reduction could be extensively implemented if it produces valuable products at those costs which are financially competitive with the present market prices. Herein, the electrochemical conversion of CO2 obtained from flue gases of a power plant to produce diesel and formic acid using a consistent techno-economic approach is presented. The first scenario analyzed the production of diesel fuel which was formed through Fischer-Tropsch processing of CO (obtained through electroreduction of CO2) and hydrogen, while in the second scenario, direct electrochemical CO2 reduction to formic acid was considered. As per the base case assumptions extracted from the previous outstanding research studies, both processes weren’t competitive with the existing fuel prices, indicating that high electrochemical (EC) cell capital cost was the main limiting component. The diesel fuel production was predicted as the best route for the cost-effective production of fuels under conceivable optimistic case assumptions, and the formic acid was found to be costly in terms of stored energy contents and has a facile production mechanism at those costs which are financially competitive with its bulk market price. In both processes, the liquid product cost was greatly affected by the parameters affecting the EC cell capital expenses, such as cost concerning the electrode area, faradaic efficiency, and current density.

The 2D single crystal WO3 nanosheets with (101) preferred orientation facets self-assembled on an FTO substrate and were applied to an aqueous electrochromic-supercapacitor.

Passive radiative cooling technologies are highly attractive in pursuing sustainable development. However, current cooling materials are often static, which makes it difficult to cope with the varying needs of all-weather thermal comfort management. Herein, a strategy is designed to obtain flexible thermoplastic polyurethane nanofiber (Es-TPU) membranes via electrospinning, realizing reversible in-situ solvent-free switching between radiative cooling and solar heating through changes in its optical reflectivity by stretching. In its radiative cooling state (0% strain), the Es-TPU membrane shows a high and angular-independent reflectance of 95.6% in the 0.25-2.5 {\mu}m wavelength range and an infrared emissivity of 93.3% in the atmospheric transparency window (8-13 {\mu}m), reaching a temperature drop of 10 {\deg}C at midday, with a corresponding cooling power of 118.25 W/m2. The excellent mechanical properties of the Es-TPU membrane allows the continuous adjustment of reflectivity by reversibly stretching it, reaching a reflectivity of 61.1% ({\Delta}R=34.5%) under an elongation strain of 80%, leading to a net temperature increase of 9.5 {\deg}C above ambient of an absorbing substrate and an equivalent power of 220.34 W/m2 in this solar heating mode. The strong haze, hydrophobicity and outstanding aging resistance exhibited by this scalable membrane hold promise for achieving uniform illumination with tunable strength and efficient thermal management in practical applications., Comment: accepted version of the manuscript published on Chemical Engineering Journal

The oxygen vacancy modulated a-WO3−x enables independent control of VIS and NIR light and has great application potential in high-performance smart windows.

Electrochromic devices (ECDs) can regulate the indoor solar radiation by adjusting optical transmissive properties, showing great commercial potential and important social value of green energy saving. However, the unsafety and high cost of Li+ based electrolyte hinder the large-scale and industrialized production of ECDs. Other metal ions have been used as electrolyte ions, but they are rarely reported in all solid state ECDs. In this study, MgF2 film is used as the solid electrolyte to construct all solid state ECD with the structure of glass/ITO/WO3/MgF2/NiO/ITO. The ECD shows the large optical modulation (∼83% at 820 nm, with 100 s durations) and fast response (19.2 s for bleaching and 8.3 s for coloring, with 25 s durations). Moreover, the ECD achieves the extreme transmittance value of colored states Tc ≈ 0%, which can give an absolute private state. This work not only indicates that MgF2 film can be an alternative to Li+ based electrolyte in all solid state ECDs, but also broadens the applications of all solid state EC smart windows to private buildings.

Dissolved oxygen (DO) level is of capital importance in the field of environmental monitoring, food fermentation, industrial production, and clinical medicine. Optical oxygen sensors with high sensitivity, accuracy, stability, and anti-jamming capability for DO content detection have provoked scientists’ attention in recent years. In this work, we selected platinum octaethylporphine (PtOEP), low-density polyethylene (LDPE), and high-density polyethylene (HDPE) as the fluorescent indicator and matrix materials, respectively. Porous LDPE/PtOEP and HDPE/PtOEP oxygen-sensing films were constructed by incorporating PtOEP in PE via the phase-separation method. The optimum parameters were obtained as follows: the concentrations of LDPE and HDPE solutions were 0.010 mg/L, and PtOEP was 8 μg. Based on the above study, the effects of different kinds of PE on the performance of the oxygen-sensing film were studied in detail, finding that the LDPE/PtOEP oxygen-sensing film had better photostability and could measure the DO concentrations of several water samples accurately.

Lithium metal, as the most ideal anode material for high energy density batteries, has been researched for several decades. However, the dendrite formation and large volume change during repetitive lithium plating/stripping lead to a serious safety issue and impede the practical application of lithium metal anode. Herein, a nanoporous Ni foam current collector with high surface area and surface flaws is constructed via a facile oxidation–reduction method. The inherent macropore structure of Ni foam can partly accommodate the volume variation during Li plating/stripping. The well-distributed nanopores on the skeleton of Ni foam can effectively reduce the local current density, regulate the uniform lithium nucleation and deposition with homogenous distribution of Li+ flux. Moreover, the surface flaws induce the formation of ring Li structures at initial nucleation/deposition processes and concave Li metal spontaneously formed based on the ring Li structures during cycling, which can direct the even Li plating/stripping. Therefore, highly stable Coulombic efficiency is achieved at 1 mA cm−2 for 200 cycles. The symmetrical cell, based on the nanoporous Ni foam current collector, presents long lifespans of 1200 and 700 h respectively at different current densities of 0.5 and 1 mA cm−2 without short circuit. In addition, the LiFePO4 full cell, with the Li metal anode based on the nanoporous Ni foam current collector, shows excellent cycling performance at 1C for 300 cycles and rate performance.

Converting solar energy efficiently into hydrogen is a promising way for renewable fuels technology. However, high-temperature heat transfer enhancement of solar thermochemical process is still a pertinent challenge for solar energy conversion into fuels. In this paper, high-temperature heat transfer enhancement accounting for radiation, conduction, and convection heat transfer in porous-medium reactor filled with application in hydrogen generation has been investigated. NiFe-Aluminate porous media is synthesized and used as solar radiant absorber and redox material. Experiments combined with numerical models are performed for analyzing thermal characteristics and chemical changes in solar receiver. The reacting medium is most heated by radiation heat transfer and higher temperature distribution is observed in the region exposed to high radiation heat flux. Heat distribution, O2 and H2 yield in the reacting medium are facilitated by convective reactive gas moving through the medium's pores. The temperature gradient caused by thermal transition at fluid-solid interface could be more decreased as much as the reaction chamber can store the transferred high-temperature heat flux. However, thermal losses due to radiation flux lost at the quartz glass are obviously inevitable.

Carbon materials with high electronic conductivity and high surface area show obvious advantage as anode material for commercial sodium-ion batteries. Here, carbon nanotubes (CNTs) with porous and disordered structures (PCNTs) are synthesized via a facile K2CO3-assisted activation method. The open porous structures (specific surface areas of 444 m2 g−1) and abundant defects (O defects content of 7.2 at%) may not only shorten the transport path of Na ion, increase contact interface between electrolyte and electrode, but also facilitate the reversible capacity of Na storage. In addition, the 3D CNT conductive network improves the electronic conductivity. PCNT anode displays a favorable reversible capacity of 255 mAh g−1 after 200 cycles at 0.1 A g−1, with an initial Coulombic efficiency of 60% and excellent rate capability of 187 mAh g−1 at 2.00 A g−1. This work gives a simple strategy for manufacturing porous CNT anode for advanced energy storage devices.

The electrochemical CO2 reduction (ECR) to produce valuable chemicals and fuels using clean energy resources is a promising and effective route to support energy storage and reduce the large CO2 concentration to avoid climate change. Among the presently adopted CO2 conversion technologies, electrochemical CO2 reduction (ECR) to valuable feedstock is presently a concern of critical research effort as a technology that can concurrently enable CO2 reduction and the storage of renewable energy. The ECR performance and economic viability are greatly influenced by the intrinsic characteristics of the catalyst employed. Many techniques have been practiced to improve the catalytic performance of heterogeneous catalysts by administering their morphology, size, crystal facets, grain boundaries, and surface defects and their integration with other synergistic constituents to fabricate nanomaterials. Presently, the fabrication of nanomaterials at the atomic level is an effective and strong technique to address the particular issues of catalytic performance and durability in ECR, by comprehending the structure–performance relationship of the nanomaterials. Herein, we present the recent technological advances with metal-derived nanomaterials, discussing the factors affecting their catalytic performance, their mechanism, and applications for the selective production of formic acid, carbon monoxide, alcohols, and hydrocarbons. Moreover, different commonly-adopted fabrication techniques for the synthesis of nanostructures have been incorporated to outline their working principles and their specialty to produce different kinds of nanostructures (nano-polyhedrons, nanowires, dendrites, and nano-frames).

Electrochromic (EC) smart windows regulate the indoor solar radiation by adjusting the optical transmittance, offering an efficient solution toward energy-saving buildings. Tungsten oxide/nickel oxide (WO3/NiO) solid-state devices are most likely to be industrialized among all the electrochromic devices (ECDs). However, there are still some problems in WO3/NiO-based solid-state electrochromic devices (ECDs), such as inflexibility, low visible light contrast, slow response speed, and poor stability in the switching process due to the charge capacity mismatch of WO3 and NiO layers. Moreover, the whole charge capacity of the ECDs depends on the charge capacity of NiO layers, which is extremely less than that of WO3 layers. Therefore, high charge capacity NiO films are in urgent demand for the fabrication of high-performance WO3/NiO solid-state ECDs with long-life stability. In order to improve these properties and overcome the mismatch problem with WO3, 2–8 wt% of H2O is added to the lithium electrolyte, which can provide hydroxide ions to participate in the electrochromic reaction of NiO films. Thus, high charge capacity (7 times enhanced than that in the anhydrous electrolyte) and high optical modulation (59.5% at 511 nm) of NiO films can be obtained. More importantly, due to the low content, OH− can be fixed on the NiO films as NiOOH, which will not erode WO3 films in devices. Hence, solid-state electrochromic devices with the structure of ITO/WO3/electrolyte/NiO/ITO were assembled, exhibiting excellent optical modulation of 62% and long-life stability up to 10 000 cycles without attenuation. Furthermore, flexible and large-area devices can also be obtained, which is important for a wide range of scientific and industrial processes.

Gallium (Ga) electrodes have been used as anodes in Li-ion batteries, due to their low-melting-point and self-healing properties. However, the use of Ga without a binder or a conductive agent together as the anode material is rare. In this study, AlCl3 was added as an additive to the electrolyte formed by [EMIm]Cl and GaCl3. The obtained binder-free Ga particles were used as the anode of the Li-ion battery; the initial specific capacity was 528.2 mA h g−1 and the initial coulombic efficiency was 97.8%. After 100 cycles, the specific capacity of discharge was 441.6 mA h g−1 at 0.1C. Ga particles obtained from ionic liquids can be used to improve the cycling stability of anodes in lithium-ion batteries.

To circumvent the imbalances of electrochemical kinetics and charge-storage capacity between Li+ ion battery anodes and capacitive cathodes in lithium-ion capacitors (LICs), dual carbon based LICs are constructed and investigated extensively. Herein, S, O dual-doped 3D net-like porous carbon (S-NPC) is prepared using waste paper as the carbon source through a facile solvothermal treatment and chemical activation. Benefiting from the combination effect of the rich S,O-doping (about 2.1 at% for S, and 9.0 at% for O), high surface area (2262 m2 g−1) and interconnected porous network structure, the S-NPC-40 material exhibits excellent electrochemical performance as both cathode material and anode material for LICs. S, O doping not only increases the pseudocapacity but also improves the electronic conductivity, which is beneficial to reduce the mismatch between the two electrodes. The S-NPC-40//S-NPC-40 LIC delivers high energy densities of 176.1 and 77.8 W h kg−1 at power densities of 400 and 20 kW kg−1, respectively, as well as superior cycling stability with 82% capacitance retention after 20 000 cycles at 2 A g−1. This research provides an efficient method to convert waste paper to porous carbon electrode materials for high performance LIC devices.

The application of flexible indium tin oxide (ITO)-free electrochromic devices (FCDs) has always been a research hotspot in flexible electronics. Recently, a silver nanowire (AgNW)-based transparent conductive film has raised great interest as an ITO-free substrate for FCDs. However, several challenges, such as the weak binding of AgNWs to the substrate, high junction resistance, and oxidation of AgNWs, remain. In this paper, a novel method for surface modification of AgNWs with

Free-standing aligned fiber is capable of providing sufficient electrochemical properties for fiber electrode without sacrificing flexibility, which is highly desirable for fiber batteries that are expected to be flexible and efficient energy storage. Here, we propose a free-standing and aligned tungstate/MXene fiber spun from their mixed liquid crystals colloid for fiber-shaped lithium/sodium-ion batteries. Benefiting from the 3D interconnected ion transport tunnels, fast charge transfer frameworks and minimum ion-path tortuosity provided by the aligned structures of 2D tungstate and MXene nanosheets, the fiber is endowed with both efficient pseudocapacitive energy storage and flexibility. As expected, the fiber delivers high reversible capacity, excellent rate capability and outstanding long-term cycling performance. Even under mechanical deformations, the fiber batteries can power the LED, digital timer, temperature-humidity meter, and smart wristband. This work may promote the further development of practical fiber batteries for wearable electronics.

In this work, the effect of coagulation bath temperature in different solvent systems [1,4-butyrolactone (GBL)/N,N-dimethylacetamide (DMAC)] on the structure and dielectric properties of polyimide (PI) films was investigated for the first time. The solubility parameter was introduced to explain the formation process of porous PI films. The results showed that the changed tendency of the dielectric constant versus temperature is opposite for the single-solvent system and cosolvent system. For a single DMAC and GBL solvent, the dielectric constants of the films decreased with increasing temperature. In contrast, the dielectric constants increased with the increase in temperature for the GBL/DMAC cosolvent system. Moreover, the measured porosities were applied to estimate the dielectric constants of the PI films. This showed that the porosity increased with increasing temperature for a single-solvent system, while it decreased for a cosolvent system. Scanning electron microscopy images suggested that the variation trends are derived from the different influences of the temperature on the structure and morphology. Thus, this study reveals the effect of coagulation bath temperature on the structure and dielectric properties of porous PI films and provides the guidance for the design and optimization of architectures for high-performance porous films.

The performance of electrochromic supercapacitors (ESCs) can be improved by the use of electrodes with high electronic conductivity and ion transport ability. Herein, two-dimensional (2D) N-doped NiO ultrathin nanosheets (N-NiO UTNSs) synthesized in situ on fluorine-doped tin oxide glass were used as bifunctional ESC electrodes. These electrodes exhibited an elevated specific capacitance (540 F g−1 at 1 A g−1), superior cycling stability (85% capacitance retention after 10,000 cycles), and good electrochromic properties (color change from colorless to black with a transmittance modulation of 73% and a coloration efficiency of up to 83.47 cm2 C−1 at 550 nm), which was ascribed to the high electronic conductivity of NiO (due to N doping) and the short ion diffusion path (due to the ultralow nanosheet thickness). To further explore the practical applications of N-NiO UTNSs, we constructed asymmetric ESCs by integrating NiO films with Fe2O3 films and revealed that these devices displayed applied voltage–dependent colors. Two charged asymmetric ESCs connected in series could light up a red light-emitting diode and changed color synchronously with charge state alteration. Thus, our results contribute to the development of Ni-based electrochromic supercapacitors exhibiting charge state-dependent color changes.

Vanadium dioxide is a well-known phase-change material on account of its unique changes of optical property, which has seen a great increase in its implementation for the regulation of thermal radiance. However, the fabrication of VO2 needs strict conditions for its narrow sliver in the phase diagram. In this paper, in situ preparation of VO2 films by high-power impulse magnetron sputtering is proposed, in which ionized flux density is used to direct the crystal growth. Besides, the surface structure and thermochromic behaviors of the deposited films are studied in detail. Furthermore, simulations are carried out for the sake of optimizing the thickness of VO2 films with the largest emissivity modulation ability, and the experimental result reveals that their tuning range reaches up to 0.32. It is believed that our work will find wide applications not only in fundamental material science but also in thermal radiance regulation.

The density and pore diameter of aluminum (Al) films have an important influence on the resultant film applications, especially in the field which require extremely high-density, uniform Al films. In this study, Al was electrodeposited from 1-ethyl-3-methyl imidazolium chloride ([EMIm]Cl) ionic liquid onto a Ni substrate using AlCl3 as the Al source. The results show that the concentration of the electrolyte was the crucial factor governing the microstructure of the electrodeposited continuous and dendrite-free Al film. The obtained continuous, dendrite-free Al film was used as the anode of a Li-ion battery. The obtained Al films delivered a first specific capacity reaching 1492 mAh g−1 in the Li-ion battery and effectively improved the corrosion resistance of the Ni substrate.

The energy and environmental crises have forced us to search for a new green energy source and develop energy storage and environmental restoration technologies. Fabrication of carbon functional materials derived from coal has attracted increasing attention in the energy storage and gas adsorption fields. In this study, an N, O-co-doped porous carbon/carbon nanotube composite was prepared by functionalizing coal-based porous carbon with carbon nanotubes (CNTs) and ionic liquid via annealing. The resulting material not only inherited the morphology of CNTs and porous carbon, but also developed a three dimensional (3D) hierarchical porous structure with numerous heteroatom groups. The N, O co-doped porous carbon/CNT composite (N, O-PC-CNTs) showed a surface area of 2164 m2 g−1, and a high level of N/O dopants (8.0 and 3.0 at%, respectively). Benefiting from such merits, N, O-PC-CNTs exhibited a rather high specific capacitance of 287 F g−1 at a current density of 0.2 A g−1 and a high rate capability (70% and 64% capacitance retention at 10 and 50 A g−1, respectively) in a three electrode system. Furthermore, an N, O-PC-CNT symmetrical supercapacitor showed a high cycling stability with 95% capacitance retention after 20 000 cycles at 20 A g−1 and an energy density of 4.5 W h kg−1 at a power density of 12.5 kW kg−1 in 6 mol L−1 KOH electrolyte. As a CO2 adsorbent, N, O-PC-CNTs exhibited a high CO2 uptake of 5.7 and 3.7 mmol g−1 at 1 bar at 273 and 298 K, respectively. Moreover, N, O-PC-CNTs showed cycling stability with 94% retention of the initial CO2 adsorption capacity at 298 K over 10 cycles. This report introduces a strategy to design a coal based porous carbon composite for use in efficient supercapacitor electrodes and CO2 adsorbents.

In this paper, we report a simple two-step hydrothermal method to improve the cyclic stability and transmittance of Prussian blue (PB) with TiO2 nanorod arrays (TNRAs). TNRAs were used as a nanostructured substrate to investigate the electrochromic properties of the PB/TNRA hybrid film. The PB/TNRA film shows excellent cyclic stability (83.8% after 1000 cycles) compared with the pure PB film (83.8% after 400 cycles). The improved cyclic stability was attributed to the increased adhesion between the PB film and the substrate and the alleviated volume expansion during the ion intercalation/deintercalation process. Moreover, the TNRA can reduce the reflectivity of the PB/TNRA film and increase the loading of PB. Therefore, the PB/TNRA film also shows a larger optical modulation (85.8% at 700 nm).