Calcium-Salt-Enhanced Fiber Membrane with High Infrared Emission and Hydrophilicity for Efficient Passive Cooling

Radiative cooling fabrics have gained significant attention for their ability to enhance comfort without consuming extra energy. Nevertheless, sweat accumulation on the skin and diminishing cooling efficiency usually exist in the reported polymer cooling membranes. Herein, we report a universal method to obtain a calcium (Ca)-salt-enhanced fiber membrane with high infrared emission and hydrophilicity for efficient passive cooling and flame retardancy. The modification by Ca salts (including CaSiO3, CaSO3, and CaHPO4) with strong infrared emission results in an improvement in hygrothermal management ability, especially for moisture absorption and perspiration regulation in hot and humid environments. As an example, the CaSiO3@PMMA fiber membrane exhibits exceptional reflectivity in the solar spectrum (∼94.5%), high emittance in the atmospheric window (∼96.7%), and superhydrophilicity with a contact angle of 31°. Under direct sunlight, the CaSiO3@PMMA membrane exhibits an obvious temperature drop of 11.7 °C and moisture management achieves an additional cooling of 8.9 °C, as further confirmed by the ability to reduce the rate of ice melting. Additionally, the composite membrane provides notable flame retardancy and UV resistance. This work paves a new path in developing new materials with perspiration management and flame retardancy for zero energy consumption cooling in hot and humid environments

Silver Nanoparticle-Induced Growth of Nanowire-Covered Porous MnO₂ Spheres with Superior Supercapacitance

We report a facile, low-cost, ultrasound-assisted synthesis of nanowire-covered porous MnO₂ spheres with superior supercapacitance at high charging rates with long-term durability. The use of catalytic silver nanoparticles is crucial to the growth mechanism in the initial stage, and the resulting silver oxides later grow the nanowires in such a way that they always terminate the wires, thus automatically covering the structures and increasing conductivity. The optimal Ag₂O–MnO₂ structures have a specific capacitance of 536.4 F/g at 5 mV/s. At a high scan rate of 100 mV/s, only 200 F/g remain for the reported carbon nanotube/MnO₂ material with an excellent capacitance at low scan rate (1230 F/g, 1 mV/s), while the Ag₂O–MnO₂ reported here still has 417.2 F/g. The material reaches a stable region of 91.3% capacitance retention over 10000 charge/discharge cycles at 5 A/g

Water-Soluble Polyaniline–Polyacrylic Acid Composites as Efficient Corrosion Inhibitors for 316SS

Water-soluble polyaniline–poly­(acrylic acid) (PANI–PAA) composites with excellent processability and electroactivity were prepared by a one-step in situ polymerization. PAA as a matrix not only improves the solubility of PANI in water but also prevents the formation of macroscopic PANI clusters. The corrosion-inhibition performance of 316 stainless steel (316SS) was evaluated in 0.5 M HCl by electrochemical measurements in the presence of PANI–PAA composites. The results show that PANI–PAA acts as a mixed-type inhibitor, and its inhibition efficiency (<i>IE</i>_(R)) increases with inhibitor concentration. The adsorption of the inhibitor on 316SS surface obeys a Langmuir adsorption isotherm. The PANI–PAA composite with an optimized concentration of 200 ppm shows marked increase in <i>IE</i>_(R), i.e., 91.68%. The enhanced efficiency is attributed to an insulating interfacial layer formed by the adsorption of PANI–PAA, which obstructs the corrosion reaction at the interface

Hierarchically MnO₂–Nanosheet Covered Submicrometer-FeCo₂O₄‑Tube Forest as Binder-Free Electrodes for High Energy Density All-Solid-State Supercapacitors

The current problem of the still relatively low energy densities of supercapacitors can be effectively addressed by designing electrodes hierarchically on micro- and nanoscale. Herein, we report the synthesis of hierarchically porous, nanosheet covered submicrometer tube forests on Ni foam. Chemical deposition and thermal treatment result in homogeneous forests of 750 nm diameter FeCo₂O₄ tubes, which after hydrothermal reaction in KMnO₄ are wrapped in MnO₂-nanosheet-built porous covers. The covers’ thickness can be adjusted from 200 to 800 nm by KMnO₄ concentration. An optimal thickness (380 nm) with a MnO₂ content of 42 wt % doubles the specific capacitance (3.30 F cm^–2 at 1.0 mA cm^–2) of the bare FeCo₂O₄-tube forests. A symmetric solid-state supercapacitor made from these binder-free electrodes achieves 2.52 F cm^–2 at 2 mA cm^–2, much higher than reported for capacitors based on similar core–shell nanowire arrays. The large capacitance and high cell voltage of 1.7 V allow high energy and power densities (93.6 Wh kg^–1, 10.1 kW kg^–1). The device also exhibits superior rate capability (71% capacitance at 20 mA cm^–2) and remarkable cycling stability with 94% capacitance retention being stable after 1500 cycles

Binary Transition-Metal Sulfides/MXene Synergistically Promote Polysulfide Adsorption and Conversion in Lithium–Sulfur Batteries

Currently, severe shuttle effects and sluggish conversion kinetics are the main obstacles to the advancement of lithium–sulfur (Li–S) batteries. Modification of the battery separator by a catalyst is a promising approach to tackle these problems, but simultaneously obtaining rich catalytic active sites, high conductivity, and remarkable stability remains a great challenge. Herein, a flower-like MXene/MoS2/SnS@C heterostructure as the functional intercalation of Li–S batteries was prepared for accelerating the synergistic adsorption-electrocatalysis of sulfur conversion. The MXene skeleton constructs a three-dimensional conductive network that anchors polysulfides and enhances charge transfer. Meanwhile, the MoS2/SnS has rich active sites for accelerating polysulfide conversion, leading to excellent electrochemical performances. A battery with MXene/MoS2/SnS@C displays an extraordinary capacity of 836.1 mAh g–1 over 200 cycles at 0.5C and demonstrates a remarkable cycling stability with a capacity attenuation of approximately 0.051% per cycle during 1000 cycles at 2C. When the sulfur loading reaches 5.1 mg cm–2, the capacity still maintains 722.4 mAh g–1 over 50 cycles. This research proposes a novel strategy to design stable catalysts for Li–S batteries with an extended lifespan

Silver Doping Mediated Route to Bimetallically Doped Carbon Spheres with Controllable Nanoparticle Distributions

We report a facile and efficient approach to prepare bimetallically doped Ag−M−carbon composites. Only if Ag nanoparticles (NPs) are embedded first into the submicrometer carbon spheres (CSs) can the second metal M (Pd, Pt, and Au) also be introduced into their interior. Especially at not too high concentrations of M-precursor ions (CM-ion), the locations and number density of the resulting NPs mirror those of the Ag NPs in/on the CSs. Therefore, the controllability of the Ag predoping allows control over the location dependent distribution of the NPs in the resulting bimetallic composites. The size and shape of the resulting NPs in the composites are largely controlled by the concentration CM-ion. The different shapes include solid core−shell and hollow NPs, as well as hedgehog-like hollow structures and dendritic aggregates. The nucleation and growth mechanisms, which differ between the different metals M, are discussed to explain the morphologies and the location dependence of the NPs in/on the CSs

Hierarchically Porous MnO₂ Microspheres Doped with Homogeneously Distributed Fe₃O₄ Nanoparticles for Supercapacitors

Hierarchically porous yet densely packed MnO₂ microspheres doped with Fe₃O₄ nanoparticles are synthesized via a one-step and low-cost ultrasound assisted method. The scalable synthesis is based on Fe²⁺ and ultrasound assisted nucleation and growth at a constant temperature in a range of 25–70 °C. Single-crystalline Fe₃O₄ particles of 3–5 nm in diameter are homogeneously distributed throughout the spheres and none are on the surface. A systematic optimization of reaction parameters results in isolated, porous, and uniform Fe₃O₄–MnO₂ composite spheres. The spheres’ average diameter is dependent on the temperature, and thus is controllable in a range of 0.7–1.28 μm. The involved growth mechanism is discussed. The specific capacitance is optimized at an Fe/Mn atomic ratio of <i>r</i> = 0.075 to be 448 F/g at a scan rate of 5 mV/s, which is nearly 1.5 times that of the extremely high reported value for MnO₂ nanostructures (309 F/g). Especially, such a structure allows significantly improved stability at high charging rates. The composite has a capacitance of 367.4 F/g at a high scan rate of 100 mV/s, which is 82% of that at 5 mV/s. Also, it has an excellent cycling performance with a capacitance retention of 76% after 5000 charge/discharge cycles at 5 A/g

Scalable Ultralight Wood-Inspired Aerogel with Vertically Aligned Micrometer Channels for Highly Efficient Solar Interfacial Desalination

An ultralight material that simultaneously combines remarkably rapid water transportation, highly efficient photothermal conversion, and excellent thermal insulation is highly desired for solar-driven interfacial desalination but was challenging. In this work, inspired by the unique natural structure of wood, we developed an ultralight aerogel by ice-templated synthesis as an integrated interfacial evaporator for solar-driven water production. The interior features vertically aligned biomimetic microscale channels facilitating rapid transportation of water molecules, while an improved photothermal interface allows high solar absorption and conversion via nonradiative relaxation and molecular vibrations. The biomimetic aerogel is ultralight with a density as low as 0.06 g/cm3, especially its fabrication is size- and shape-programmable as a whole and easily scalable. Additionally, the outstanding thermal insulation of the aerogel focuses heat precisely at the evaporation interface, reducing ineffective heat loss, while the uniformly distributed large-sized channels promote the dynamic convection of high concentration salt ions on the evaporator surface. Consequently, the evaporator shows broadband light absorption of 92.7%, leading to a water evaporation rate reaching 4.55 kg m–2 h–1 under 3 simulated solar irradiations, much higher than that of other reported evaporators with randomly distributed pores. This work provides new insight into advanced hybrid aerogels for highly efficient and durable solar-driven interfacial desalination systems

Bioinspired Polymer Films with Surface Ordered Pyramid Arrays and 3D Hierarchical Pores for Enhanced Passive Radiative Cooling

Passive radiative cooling (PRC) has been acknowledged to be an environmentally friendly cooling technique, and especially artificial photonic materials with manipulating light–matter interaction ability are more favorable for PRC. However, scalable production of radiative cooling materials with advanced biologically inspired structures, fascinating properties, and high throughput is still challenging. Herein, we reported a bioinspired design combining surface ordered pyramid arrays and internal three-dimensional hierarchical pores for highly efficient PRC based on mimicking natural photonic structures of the white beetle Cyphochilus’ wings. The biological photonic film consisting of surface ordered pyramid arrays with a bottom side length of 4 μm together with amounts of internal nano- and micropores was fabricated by using scalable phase separation and a quick hot-pressing process. Optimization of pore structures and surface-enhanced photonic arrays enables the bioinspired film to possess an average solar reflectance of ∼98% and a high infrared emissivity of ∼96%. A temperature drop of ∼8.8 °C below the ambient temperature is recorded in the daytime. Besides the notable PRC capability, the bioinspired film exhibits excellent flexibility, strong mechanical strength, and hydrophobicity; therefore, it can be applied in many complex outdoor scenarios. This work provides a highly efficient and mold replication-like route to develop highly efficient passive cooling devices