Calcination In Air Research Articles

Promoted electrocatalytic water splitting by regulating the concentration of oxygen vacancies

Among the many methods of hydrogen production, the electrolysis of water has a broad prospect. In this experiment, NiCo2O4 nanosheets with different degrees of oxidation were synthesized on nickel foam by the hydrothermal method, air calcination and reduction steps. The experimental results show that reduction treatment significantly improved the catalytic activity of NiCo2O4 materials under alkaline medium conditions of 1.0 mol/L KOH. V–NiCo2O4-4 shows better catalytic activity with an overpotential of 285 mV and 340 mV for the oxygen evolution reaction (OER) at 10 mA cm−2 and 50 mA cm−2, respectively. The better catalytic activity of V–NiCo2O4-4 is mainly assigned to the flower-like structure of the catalyst surface and the moderate reduction of NaBH4, resulting in more oxygen vacancies and active sites. Density functional theory calculation also indicates that the V–NiCo2O4-4 material has a stronger water absorption energy (0.75 eV) compared to the V–NiCo2O4-2 and V–NiCo2O4-6 materials, which provides a new foundation for the construction of binder-free high-performance electrodes for water splitting.

Breaking the activity-stability trade-off of Au catalysts by depth-controlled TiO2 nanotraps

The sintering of nanoparticles has always been a great challenge for supported Au catalysts. Herein, we fabricate a depth-controlled TiO2 nanotrap via area-selective atomic layer deposition (ALD) method to balance the activity and anti-sintering properties of Au nanoparticles. Au nanoparticles anchored by a 2.31 nm deep TiO2 nanotrap prepared by 25 ALD cycles of TiO2 exhibit the best overall activity for CO oxidation, where the depth of TiO2 nanotrap is close to the geometric radius of Au nanoparticle. It exhibits enhanced sintering resistance while retaining an activity similar to that of pure Au catalyst. The average size of sintered Au (8.4 ± 2.7 nm) is three times smaller than that of pure Au catalyst (21.1 ± 7.1 nm) after calcination in air at 700 °C. The performance of TiO2 nanotrapped Au catalyst breaks the conventional trade-off between the activity and anti-sintering capability of Au by exposing active sites, and hindering Au migration-coalescence simultaneously, which serves as a promising strategy to design highly stable Au catalysts.

Temperature Ramp Strategy for Regulating Oxygen Vacancies in NiCo2O4 Nanoneedles Towards Enhanced Electrocatalytic Water Splitting.

The oxide-based systems often suffer from higher overpotentials compared to transition metal sulphides and phosphides for the electrochemical hydrogen evolution reaction. Interestingly, the generation of oxygen vacancy has been seen as strategy for further activating transition metal oxides (NiCo2O4 as a model system) for electrochemical watersplitting. Herein, we employ the temperature ramp strategy (ambient air calcination) for the generation of oxygen vacancies in NiCo2O4 (NCO) towards tuning of electrocatalytic enhancements. The NiCo2O4 synthesized at temperature ramp rates of 2 (NCO-2), 5 (NCO-5), and 10ºC/ min (NCO-10) depicts contrasting structural features and varying Ni:Co:O surface composition. The decrease in the crystallite size and converse trend in the particle strain were observed from NCO-2 to NCO-10. Interestingly, the surface Ni:Co:O ratios of 1:0.78:3.6, 1:0.81:3.3, and 1:0.69:2.8 for NCO-2, NCO-5, and NCO-10, respectively, were observed. The reduced relative oxygen ratio in the latter implies generation of ample amount of oxygen vacancy defects. HER performance depicts a consistent trend with enhanced oxygen defect concentration with the overpotential requirement of 700, 647, and 597 mV for NCO-2, NCO-5, and NCO-10, respectively, for the generation of a cathodic current of 25 mA cm-2. The same trend in an electrocatalytic enhancement is observed for other cathodic currents.

Ultrathin Carbon Coating and Defect Engineering Promote RuO2 as an Efficient Catalyst for Acidic Oxygen Evolution Reaction with Super‐High Durability

AbstractDeveloping acid‐stable electrocatalysts with high activity for the oxygen evolution reaction (OER) is of paramount importance for many energy‐related technologies. This work reports that ultrathin nitrogen‐doped carbon coated oxygen‐vacancy (Vo·) rich RuO2 nanoparticles on carbon nanotubes (CNTs) (NC@Vo·‐RuO2/CNTs‐350), synthesized through the controlled calcination in air, is an efficient acid‐stable electrocatalyst for the OER. It only needs an overpotential of 170.0 mV to drive 10.0 mA cm−2 and shows excellent stability with no distinguishable activity loss observed for >900 h. Its mass activity is >110 times higher than the commercial RuO2. In particular, an electrolyzer assembled with this catalyst shows a record‐low cell voltage of 1.45 V to deliver 10.0 mA cm−2 and exhibits a low performance drop for >1000 h. The NC@Vo·‐RuO2/CNTs‐350 also shows super‐high catalytic activities and excellent stabilities for OER in neutral and alkaline media. DFT calculations indicate that its high catalytic activity mainly arises from the strong electronic coupling between RuO2 and NC/CNTs, which increases the oxidation state and catalytic activity of Ru at the active site and improves the stabilities of lattice oxygen and surface Ru during the OER processes. The presence of Vo· can strengthen the electronic coupling between RuO2 and NC/CNTs.

Systematic Investigation on Supported Gold Catalysts Prepared by Fluorine-Free Basic Etching Ti3AlC2 in Selective Oxidation of Aromatic Alcohols to Aldehydes.

Conventional methods to prepare supported metal catalysts are chemical reduction and wet impregnation. This study developed and systematically investigated a novel reduction method based on simultaneous Ti3AlC2 fluorine-free etching and metal deposition to prepare gold catalysts. The new series of Aupre/Ti3AlxC2Ty catalysts were characterized by XRD, XPS, TEM, and SEM and were tested in the selective oxidation of representative aromatic alcohols to aldehydes. The catalytic results demonstrate the effectiveness of the preparation method and better catalytic performances of Aupre/Ti3AlxC2Ty, compared with those of catalysts prepared by traditional methods. Moreover, this work presents a comprehensive study on the influence of calcination in air, H2, and Ar, and we found that the catalyst of Aupre/Ti3AlxC2Ty-Air600 obtained by calcination in air at 600 °C performed the best, owing to the synergistic effect between tiny surface TiO2 species and Au NPs. The tests of reusability and hot filtration confirmed the catalyst stability.

Effect of surface impregnation of Gd3+ over Bi2O3 for the degradation of bisphenol A and chlorophenoxy herbicides in natural sunlight exposure

In order to address the issues of the short life span of excitons, the limited generation of reactive oxygen species due to the unsuitable conduction band edge, and inadequate photocatalytic activity, the surface of Bi2O3 was altered by the surface impregnation of Gd3+ that converted to Gd2O3 by air calcination. The FESEM and XRD analysis revealed the uniform distribution of 50–80 nm Gd2O3 particles at the surface of Bi2O3 without affecting the skeletal arrangement. The improved absorption in the visible region and the red shift in the band gap values identified the lowering of the conduction band edge formed by the merger of Bi3+ (6p) and Gd3+ (4 f) orbitals. The supporting role of Gd3+ entities in prolonging the life span of the excitons was revealed by the sequentially decreasing intensity with the enhanced surface loading in the PL analysis. The retention of the oxidation states was assessed by XPS analysis. As compared to Bi2O3, the as-synthesized materials exhibited significantly enhanced photocatalytic activity in natural sunlight exposure for the removal/mineralization of potential organic contaminants i.e., Bisphenol A (BPA), and chlorophenoxy herbicides (2,4-dichlorophenoxyacetic acid (2,4-D), and 4-methyl, 2-chlorophenoxyacetic acid (MCPA)). The synthesized 2 % Gd3+ impregnated Bi2O3 photocatalyst showed remarkable photocatalytic activity of ∼98 %, ∼91 %, and ∼86 % for the degradation of 2,4-D, MCPA, and BPA, respectively, in 360 min of sunlight exposure. Total organic carbon (TOC) measurements were used to estimate the mineralization efficiency of impregnated materials and the observed percentage mineralization efficiency was ∼76 %, ∼74 %, and ∼70 % for 2,4-D, MCPA, and BPA pollutants, correspondingly. The data extracted from the analytical tools deliver deep insight into the supporting role of rare earth metals in the field of photocatalytic water decontamination.

Alkali-assisted engineering of ultrathin graphite phase carbon nitride nanosheets with carbon vacancy and cyano group for significantly promoting photocatalytic hydrogen peroxide generation under visible light: Fast electron transfer channel

Exfoliating bulk graphite phase carbon nitride (g-C3N4) into 2D nanosheets is considered to be an effective method to enhance its photocatalytic activity. However, optical absorption capacity of the exfoliated g-C3N4 nanosheets are lower than that of the original bulk g-C3N4 due to the quantum size effect. Here, the ultrathin graphite phase carbon nitride nanosheets containing both carbon vacancy and cyano group (UCNS580) were prepared by two-step calcination in air with the assistance of KOH. The formation and position of carbon vacancy and cyano group were first investigated and determined. The simultaneous introduction of carbon vacancy and cyano group not only improved light absorption range and intensity of g-C3N4 nanosheets, but also more importantly constructed a fast transfer channel for photogenerated electrons, further enhancing the separation efficiency and migration ability of photogenerated carriers. The cyano group as the accumulation center of photogenerated electrons and the oxygen adsorption center increased the proportion of one-step two-electrons reaction path to efficiently generate H2O2. As a result, UCNS580 exhibited highly boosted H2O2 generation activity, its H2O2 production yield for 6 h reached 939 µmol/L and the formation rate was up to 4167 µM h−1 g−1, which was in priority in the reported literature under the same conditions.

Activity–Stability Trends of the Sb-SnO2@RuOx Heterostructure toward Acidic Water Oxidation

Accomplishments of enhanced activity and durability are a major concern in the design of catalysts for acidic water oxidation. To date, most studied supported metal catalysts undergo fast degradation in strongly acidic and oxidative environments due to improper controlling of the interface stability caused by their lattice mismatches. Here, we evaluate the activity-stability trends of in situ crystallized antimony-doped tin oxide (Sb-SnO2)@RuOx (Sb-SnO2@RuOx) heterostructure nanosheets (NSs) for acidic water oxidation. The catalyst prepared by atomic layer deposition of a conformal Ru film on antimony-doped tin sulfide (Sb-SnS2) NSs followed by heat treatment highlights comparable activity but longer stability than that of the ex situ catalyst (where Ru was deposited on Sb-SnO2 followed by heating). Air calcination for in situ crystallization allows the formation of hierarchical mesoporous Sb-SnO2 NSs from as-prepared Sb-SnS2 NSs and parallel in situ transformation from Ru to RuOx, resulting in a compact heterostructure. The significance of this approach significantly resists corrosive dissolution, which is justified by the enhanced oxygen evolution reaction (OER) stability of the catalyst compared to most of the state-of-the-art ruthenium-based catalysts including Carbon@RuOx (which shows ∼10 times higher dissolution) as well as Sb-SnO2@Com. RuOx and Com. RuO2. This study demonstrates the controlled interface stability of heterostructure catalysts toward enhancing OER activity and stability.

Temperature-controlled dual-selectivity nitric oxide/acetone sensor constructed from mesoporous SnO2 tubes doped by biomass-derived graphitic carbon

How to achieve good dual-functional selectivity of metal oxide-based sensors to harmful gases remains challenge due to few relevant reports. To this purpose, we selected waste willow catkins as structure-oriented template and carbon source to controllably prepare biomorphic GC/SnO2-500 sensing material by air calcination of 500 °C. Its tubular morphology is cross-linked by 3.51 wt% biomass-derived graphitic carbon (GC) and small-size nanoparticles. It has relatively large specific surface area, uniform mesopore distribution and rich oxygen vacancies. The synergistic effect of above positive factors promotes the rapid gas transport to sensing layer, and also increases the reactive sites and its resistance modulation ability, thus achieving good dual-functional selectivity. At 92 °C, GC/SnO2-500 sensor displays large response value of 802 to 10 ppm NO, and exhibits a good response towards 100 ppm acetone at 217 °C (S = 22). Both of the indexes are better than those of most corresponding gas sensors reported presently. Meanwhile, the sensor has short response time, satisfactory long-term stability and humidity tolerance. Moreover, portable temperature-dependent dual-functional gas-sensing mechanism is also discussed.

Controlled preparation of spinel CoCr2O4 nanocrystals with variable proportions of mixed redox couplings for enhanced sensing to hydrogen peroxide

Chromium-based spinels with multiple mixed valence states have been considered as promising electrocatalysts. However, they are rarely reported as electrochemical sensors. Herein, spinel CoCr2O4 nanocrystals with mixed redox couplings were controllably synthesized through a simple sol-gel method followed by air calcination at 500 °C and 600 °C. The X-ray photoelectron spectrum analyses reveal that CoCr2O4-500 and CoCr2O4-600 products possess different surface ratios of Co3+/Co2+ and Cr3+/Cr2+. Meanwhile, non-enzymatic H2O2 electrochemical sensors were successfully fabricated by drop-coating the aforementioned nanomaterials onto the surface of bare glassy carbon electrode (GCE). Amongst, CoCr2O4-500/GCE shows high sensitivity (1016 μA mM-1 cm-2), low detection limit (150 nM) and wide detection range to H2O2 in 0.1 M NaOH solution. These important indicators are better than those of CoCr2O4-600/GCE. It is also the first time to achieve highly sensitive detection of H2O2 by pure chromite spinels so far. Such excellent electrochemical sensing performance stems from the synergistic effect of its large apparent electrode area, high electrical conductivity and proper surface ratio of mixed redox couplings for Co3+/2+/Cr3+/2+. Moreover, it also exhibits good selectivity, stability and recovery rate to trace H2O2 in milk whey, mouthwash and contact lens cleaning solution.

A Study on the Synthesis and Proton Transport Behavior of Multilayered ZSM-5 Zeolite Nanosheet Membranes Laminated on Polymer Substrates

Single crystalline ZSM-5 ZNs with thicknesses around 6 nm were obtained by secondary growth of silicalite nanoparticles using diquaternary bis-1,5(tripropyl ammonium) pentamethylene diiodide (dC5) as a structure-directing agent (SDA). The dC5 could be effectively removed from the ZN pores by either high-temperature calcination or UV irradiation in air at room temperature but not by the piranha solution treatment. Ultrathin ZN-laminated membranes (ZNLMs) were fabricated by sandwiching a UV-activated multilayered ZN film between two recast Nafion® layers (ZNLM-Nafion) and by filtration coating from a suspension of thermally activated ZNs on a nonionic porous PVDF (ZNLM-PVDF). The ZNLMs on both supports demonstrated the ability of highly proton-selective ion conduction with low resistances in aqueous electrolyte solutions. The ZNLM-PVDF with PVDF binder was structurally stable, and it achieved a comparably low ASR but much higher proton selectivity compared with a Nafion membrane of same overall thickness. However, detachment between the ZNLM and Nafion layers occurred when the ZNLM-Nafion operated in aqueous electrolyte solutions. Results of this study show the potential for developing ZNLMs as efficient proton-conducting membranes without using expensive ionic polymer matrices. However, the development of polymer-supported ZNLMs is hindered by the current inefficiency in preparing well-dispersed suspensions of open-pore ZNs. Future development of efficient methods for synthesizing open-pore ZNs in dispersed states is key to realizing high-performance ZNLMs on polymers.

Benzylic Alcohol Oxidation using Copper Oxide/ZincOxide/Zirconia Nanocomposite Catalysts.

Herein, we have developed a nanocomposite catalyst for organic transformation. The catalysts are synthesized based on CuO/ZnO/ZrO2 materials through the coprecipitation method followed by calcination in air at 500 °C for 5 h. The physicochemical characterization using TGA, XRD, SEM and N2 -physisorption at -196 °C was carried out for all the prepared catalysts. Nanocomposite catalyst with Cu/Zn=1 : 1 showed the smallest particle size and largest surface area among all the other investigated catalysts. Under ideal reaction conditions, this new heterogenous catalyst has demonstrated its excellent efficacy for the oxidation of benzylic alcohol and can be successfully used in up to three catalytic cycles with little loss of catalytic activity.

Fabrication of magnetic bifunctional composite via anchoring CoY on waste heating pad as a cycling material for peroxymonosulfate activation to degrade p-arsanilic acid and simultaneously eliminate secondary As(V)

Herein, waste heating pad, which mainly contains iron and vermiculite components after calcination in air, was used to support cobalt-yttrium bimetallic oxide for the first time. The magnetic material (IV@CoY) was applied for the activation of peroxymonosulfate (PMS) to simultaneously realize the removal of p-arsanilic acid (p-ASA) and the secondary inorganic arsenic (As(V)). 50 µM p-ASA was completely degraded in the system of IV@CoY (0.2 g/L) and PMS (0.5 mM) within 7 min, and about 99 % of the produced As(V) was adsorbed within 150 min. Electrochemical experiments illustrated that IV@CoY possessed the superior conductivity as compared to CoY, which greatly boosted PMS activation. The pseudo-first-order rate constant (kIV@CoY) was high up to 0.873 min−1, which was 7.6 times larger than kCoY (0.115 min−1). Catalytic mechanism analyses revealed that the produced SO4•−, •OH and 1O2 participated in the oxidation of p-ASA and As(III). The adsorption of the produced As(V) was achieved by ion exchange with −OH/CO32− on the surface of IV@CoY. The degradation pathways of p-ASA were further proposed on the basis of the detection of its intermediate products. Initial pH exerted a significant effect on the degradation-adsorption reaction and weak acidic or neutral condition was beneficial to the removal of p-ASA and As(V). To evaluate the practical application potential of IV@CoY, the disposal of p-ASA and secondary As(V) were also carried out in real water samples. Furthermore, IV@CoY was consecutively used for 5 times, and almost 100% degradation of p-ASA and over 97% adsorption of inorganic arsenic were still achieved even in the fifth round, which prove its high stability and reusability. Our results fully demonstrate that the magnetic IV@CoY is a promising catalyst to activate PMS for eliminating organoarsenic from water.

Identification of Nano-Metal Oxides That Can Be Synthesized by Precipitation-Calcination Method Reacting Their Chloride Solutions with NaOH Solution and Their Application for Carbon Dioxide Capture from Air-A Thermodynamic Analysis.

Several metal oxide nanoparticles (NPs) were already obtained by mixing NaOH solution with chloride solution of the corresponding metal to form metal hydroxide or oxide precipitates and wash-dry-calcine the latter. However, the complete list of metal oxide NPs is missing with which this technology works well. The aim of this study was to fill this knowledge gap and to provide a full list of possible metals for which this technology probably works well. Our methodology was chemical thermodynamics, analyzing solubilities of metal chlorides, metal oxides and metal hydroxides in water and also standard molar Gibbs energy changes accompanying the following: (i) the reaction between metal chlorides and NaOH; (ii) the dissociation reaction of metal hydroxides into metal oxide and water vapor and (iii) the reaction between metal oxides and gaseous carbon dioxide to form metal carbonates. The major result of this paper is that the following metal-oxide NPs can be produced by the above technology from the corresponding metal chlorides: Al2O3, BeO, CaO, CdO, CoO, CuO, FeO, Fe2O3, In2O3, La2O3, MgO, MnO, Nd2O3, NiO, Pr2O3, Sb2O3, Sm2O3, SnO, Y2O3 and ZnO. From the analysis of the literature, the following nine nano-oxides have been already obtained experimentally with this technology: CaO, CdO, Co3O4, CuO, Fe2O3, NiO, MgO, SnO2 and ZnO (note: Co3O4 and SnO2 were obtained under oxidizing conditions during calcination in air). Thus, it is predicted here that the following nano-oxides can be potentially synthesized with this technology in the future: Al2O3, BeO, In2O3, La2O3, MnO, Nd2O3, Pr2O3, Sb2O3, Sm2O3 and Y2O3. The secondary result is that among the above 20 nano-oxides, the following five nano-oxides are able to capture carbon dioxide from air at least down to 42 ppm residual CO2-content, i.e., decreasing the current level of 420 ppm of CO2 in the Earth's atmosphere at least tenfold: CaO, MnO, MgO, CdO, CoO. The tertiary result is that by mixing the AuCl3 solution with NaOH solution, Au nano-particles will precipitate without forming Au-oxide NPs. The results are significant for the synthesis of metal nano-oxide particles and for capturing carbon dioxide from air.

Co3-xFexO4 inverse opals with tunable catalytic activity for high-performance overall water splitting.

The development of earth-abundant and high-performance bifunctional catalysts for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in alkaline electrolytes is required to efficiently produce hydrogen by electrochemical water splitting, but remains a challenge. We have fabricated mesoporous cobalt iron oxide inverse opals (m-CFO IO) with different mole ratios of cobalt and iron by a wet chemical method using polystyrene beads as a hard template, followed by calcination in air. The performance of the m-CFO IO as OER and HER electrocatalysts was investigated. The as-prepared catalyst with equal concentrations of Fe and Co exhibits remarkable OER and HER performances with low overpotentials of 261 and 157 mV to attain 10 mA cm-2 and small Tafel slopes of 63 and 56 mV dec-1, respectively. An alkaline water electrolyzer with a two-electrode configuration achieves 10 mA cm-2 at 1.55 V with excellent long-term stability, outperforming the combination of noble metal IrO2 and Pt/C benchmark catalysts. The superior catalytic performance is ascribed to the synergistic effects of particle size, crystallinity, oxygen efficiency, a large number of active sites, and the large specific surface area of the porous inverse opal structure.

Construct NiSe/NiO Heterostructures on NiSe Anode to Induce Fast Kinetics for Sodium-Ion Batteries

It is of great significance to design and innovate electrode materials with unique structures to effectively optimize the electrochemical properties of the secondary battery. Herein, inspired by neuron networks, an ingenious synthesis is proposed to fabricate NiSe with multidimensional micro-nano structures, followed by in situ construction of NiSe/NiO heterostructures via a temporary calcination. The major structure of bulk NiSe synthesized by the solvothermal method is 3-dimensional micron cluster spherical particles interwoven by uniform one-dimensional nanofibers. Such structures possess the synergistic advantages of nano and micro materials. After a temporary calcination in air, NiSe/NiO heterostructures should be formed in the bulk NiSe, which provides a built-in electric field to enhance diffusion kinetics of sodium ions. This special neural-like network and heterojunction structures ensure the excellent structural stability combined with rapid kinetics of the electrode, releasing 310.9 mAh g −1 reversible capacity after 2,000 cycles at 10 A g −1 . Furthermore, the electrochemical storage and ion transport mechanisms are elaborated by electrochemical analysis and theoretical calculation in more detail.

Enhancing reductive C-N coupling of nitrocompounds through interfacial engineering of MoO2 in thin carbon layers.

In this study, we developed an approach by coating silica nanospheres with polydopamine and metal precursor, followed by carbonization to create interfacial engineered MoO2. The presence of numerous crystal interfaces and metal-carbon interactions resulted in a remarkable enhancement of C-N coupling activity and stability of catalyst compared to one obtained by air calcination.

Hydrothermal synthesis of a bimetallic metal-organic framework (MOF)-derived Co3O4/SnO2 composite as an effective material for ethanol detection.

This study utilized a hydrothermal method and air calcination to prepare a bimetallic metal-organic framework (MOF) derived Co3O4/SnO2 nanocomposite material, which was employed as a sensing material for ethanol detection. The structure, elemental composition, and surface morphology of Co3O4/SnO2 nanocomposite materials were defined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Compared to SnO2 nanoparticles derived from metal-organic frameworks, the bimetallic metal-organic framework-derived Co3O4/SnO2 nanocomposite material exhibits significantly superior ethanol sensing performance. At 225 °C, the response value (R = Ra/Rg) to 100 ppm ethanol is 135, demonstrating excellent repeatability, selectivity and stability. Gas sensitivity assessment findings indicate that the 3 at% (Co/Sn) Co3O4/SnO2 nanocomposite is an excellent gas sensing material, providing strong technical support for ethanol detection and environmental monitoring.

Elastic and compressible Al2O3/ZrO2/La2O3 nanofibrous membranes for firefighting protective clothing

Developing ceramic nanofibrous membranes for the thermal insulation layer of firefighting protective clothing is vital. However, previous ceramic nanofibrous membranes were brittle and easy to break during service in high-temperature environments. The lack of elastic and compressible properties has limited the high-end applications of ceramic nanofibrous membranes. In this work, elastic and compressible Al2O3/ZrO2/La2O3 nanofibrous membranes were fabricated via sol–gel electrospinning and calcination in air at different temperatures. The as-fabricated Al2O3/ZrO2/La2O3 nanofibrous membranes can maintain excellent elasticity and compressibility in the temperature ranging from −196 to 1400 °C. Moreover, they have low thermal conductivity and high working temperatures. These favorable characteristics make the Al2O3/ZrO2/La2O3 nanofibrous membranes a promising candidate for the thermal insulation layer of firefighting protective clothing.

In situ growing fusiform SnO2 nanocrystals film on carbon fiber cloth as an efficient and flexible microwave absorber

Developing highly efficient flexible microwave absorber is of great significance for wearable electronics and aerospace applications. In this work, the fusiform SnO2 nanocrystals film in situ grown on flexible carbon fiber cloth is rationally designed and fabricated through combining air calcination and hydrothermal synthesis. X-ray photoelectron spectrum confirms fusiform SnO2 nanocrystals film and carbon fiber cloth are effectively integrated with strong chemical bonds of COSn. The as-prepared composite exhibits strong reflection loss of −49.1 dB (2.6 GHz) and wide effective absorption bandwidth of 5.8 GHz (11.6–17.4 GHz) with a thin matched thickness of 1.6 mm, surpassing to pure carbon fiber cloth and many SnO2/carbon-based microwave absorbers. The efficient performance originates from well-matched characteristic impedance and multifarious electromagnetic attenuation mechanisms, i.g., dipole orientation polarization, interfacial polarization relaxation, conductive loss, and multiple reflections/scatterings. Especially, differential charge density calculation reveals the uneven charge distribution at SnO2/C interface, which is believed to remarkably enhance interfacial polarization relaxation and contribute to microwave absorption. Our results illustrate that the ingenious integration of nanomaterials on carbon fiber cloth promises a way to achieve efficient and flexible microwave absorbers.