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This work prepared a novel biochar from willow catkins (WC) by a two-step pyrolysis and KOH activate to adsorb tetracycline hydrochloride (TCH) in water. The effects of pyrolysis temperature and activator amount on adsorption capacity were investigated. The results showed that the adsorbent with the largest adsorption capacity, which was named as KWCBC, was obtained when the pyrolysis temperature of the first and second stage was 600 °C and 800 °C, and the dry mass ratio of KOH and WC biochar was 4. After KOH activation and two-step pyrolysis, the pore structure and adsorption capacity of biochar were greatly improved. KWCBC possessed developed pore structure and large specific surface area (2402.31 m2/g), which was conducive to the adsorption process. KWCBC had superior stability against the changes of initial pH and foreign ions. Moreover, KWCBC showed favorable application potential in actual water and excellent regeneration performance. The adsorption behavior was well explained by Freundlich isotherm model and pseudo-second order kinetic model. The maximum adsorption capacity of TCH on KWCBC determined by the Langmuir model was up to 1242.31 mg/g at 45 °C. The major mechanisms including pore filling, hydrogen bonding, electrostatic effects and π-π interactions were involved in the adsorption process. The findings obtained in this study can provide valuable insights into the adsorption properties and mechanisms of KWCBC, which may assist in developing effective adsorbents for TCH removal from water. [ABSTRACT FROM AUTHOR]

In this study, willow catkins/MoS2 nanoparticles (denoted as WCMSs) have been prepared using a hydrothermal method. The WCMSs were modified with oleic acid (OA) to improve dispersion in base oil. The friction and wear properties of WCMSs in liquid paraffin (LP) for steel balls were investigated using a four-ball wear tester. The results have shown that at a high reaction temperature, willow catkins (being used as a template) and urea (being used as a nitrogen resource) can effectively decrease the wear scar diameters (WSDs) and coefficients of friction (COFs). At a concentration of 0.5 wt.%, the WSD and COF of steel balls, when lubricated using LP containing modified WCMS with urea, decreased from 0.65 mm and 0.175 of pure LP to 0.46 mm and 0.09, respectively. The addition of urea and hydroxylated catkins can generate a significant number of loose nano-sheets and even graphene-like sheets. The weak van der Waals forces, decreasing the shear forces that the steel balls must overcome, provide effective lubrication during rotation. On the other hand, the tribo-films containing MoS2, FeS, azide, metal oxides and other compounds play important roles in reducing friction and facilitating anti-wear properties. [ABSTRACT FROM AUTHOR]

Recently, efficient decontamination of water and wastewater have attracted global attention due to the deficiency in the world's water sources. Herein, activated carbon (AC) derived from willow catkins (WCs) was successfully synthesized using chemical modification techniques and then loaded with different weight percentages of nickel ferrite nanocomposites (10, 25, 45, and 65 wt.%) via a one-step hydrothermal method. The morphology, chemical structure, and surface composition of the nickel ferrite supported on AC (NFAC) were analyzed by XRD, TEM, SEM, EDX, and FTIR spectroscopy. Textural properties (surface area) of the nanocomposites (NC) were investigated by using Brunauer–Emmett–Teller (BET) analysis. The prepared nanocomposites were tested on different dyes to form a system for water remediation and make this photocatalyst convenient to recycle. The photodegradation of rhodamine B dye was investigated by adjusting a variety of factors such as the amount of nickel in nanocomposites, the weight of photocatalyst, reaction time, and photocatalyst reusability. The 45NFAC photocatalyst exhibits excellent degradation efficiency toward rhodamine B dye, reaching 99.7% in 90 min under a simulated source of sunlight. To summarize, NFAC nanocomposites are potential photocatalysts for water environmental remediation because they are effective, reliable, and reusable. [ABSTRACT FROM AUTHOR]

In this study, willow catkins/MoS2 nanoparticles (denoted as WCMSs) have been prepared using a hydrothermal method. The WCMSs were modified with oleic acid (OA) to improve dispersion in base oil. The friction and wear properties of WCMSs in liquid paraffin (LP) for steel balls were investigated using a four-ball wear tester. The results have shown that at a high reaction temperature, willow catkins (being used as a template) and urea (being used as a nitrogen resource) can effectively decrease the wear scar diameters (WSDs) and coefficients of friction (COFs). At a concentration of 0.5 wt.%, the WSD and COF of steel balls, when lubricated using LP containing modified WCMS with urea, decreased from 0.65 mm and 0.175 of pure LP to 0.46 mm and 0.09, respectively. The addition of urea and hydroxylated catkins can generate a significant number of loose nano-sheets and even graphene-like sheets. The weak van der Waals forces, decreasing the shear forces that the steel balls must overcome, provide effective lubrication during rotation. On the other hand, the tribo-films containing MoS2, FeS, azide, metal oxides and other compounds play important roles in reducing friction and facilitating anti-wear properties.

Utilization of carbon materials for harvesting solar energy is a green, feasible, sustainable, and promising way to manufacture freshwater from sewage and seawater. However, sunlight absorption efficiency, light to thermal conversion efficiency, and expensive cost are still limitations for large‐scale solar steam generation. Here, a solar steam evaporator which is fabricated by carbonized willow catkins films and activated by different metal chlorides under nitrogen at 800 °C is demonstrated. Under the light irradiation intensity of one sun (1000 W m−2), water evaporation rate of the prepared evaporator is up to ≈2.17 kg m−2 h−1, and the surface temperatures reach up to 50 and 91.7 °C under water‐saturated and dry situations, respectively, indicating good steam generation ability and heat localization performance of the fabricated evaporator. The SEM, BET, DSC, and ICP‐MS results show that such a high water evaporation rate of the prepared carbon materials is due to the typical tubular micro‐structure, which decreases water enthalpy of evaporation and the water evaporation in the form of molecular clusters. This method of carbonized and activated willow catkins films provides a sustainable way for efficiently harvesting solar energy to produce fresh water from seawater and sewage. [ABSTRACT FROM AUTHOR]

Oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are three paramount electrochemical processes for renewable energy conversion technologies consisting of fuel cells, metal-air batteries and water splitting devices. There remains a big challenge to fabricate low-cost and durable electrocatalysts with optimal catalytic performance for ORR, OER and HER. 3D hollow porous carbon based materials with attractive structural properties are usually constructed as promising candidates for electrocatalysis. Herein, we report a reactable ionic liquid (IL) in situ -induced synthesis of Fe 3 O 4 nanoparticles decorated willow catkins derived N-doped 3D hollow porous carbon microtubes multifunctional electrocatalyst (Fe 3 O 4 /NCMTs-800(IL)). IL shows a huge advantage of control in synthesizing small size Fe 3 O 4 nanoparticles, achieving uniform nanoparticles on hollow carbon microtubes owing to the interaction between the IL and carbon substrate. The Fe 3 O 4 /NCMTs-800(IL) electrocatalyst affords a positive half-wave potential for ORR, small overpotential for the OER and HER, and high stability for water splitting activity. The as-obtained electrocatalyst exhibits efficient and robust electrocatalytic performance can be ascribed to the special 3D porous structure and the synergistic effect of Fe 3 O 4 and doped-N species. The approach indicates the great electrochemical energy applications for biomass and ionic liquids. Image 1 • Ionic liquid induced Fe 3 O 4 nanoparticles decorated on N-doped carbon substrate. • Willow catkins serve as the precursors for 3D hollow porous carbon microtubes. • The Fe 3 O 4 /NCMTs-800(IL) electrocatalyst shows excellent electrocatalytic performance. [ABSTRACT FROM AUTHOR]

Biomass is receiving considerable attention because of its significant advantages as a sustainable and renewable material. Willow catkins, which have a single-walled microtubular structure are used as both a template and a precursor for synthesizing porous graphitic carbon microtubes (PGCMT) induced by the simultaneous activation–graphitization of K 4 Fe(CN) 6 . In addition to providing low-resistant pathways and short ion diffusion channels, as-obtained PGCMT with tubular structure also serves as an ideal platform for anchoring MnO 2 . The PGCMT/MnO 2 composite electrode obtained by MnO 2 electrodeposition expressed excellent electrochemical performance, including a significantly enhanced specific capacitance (550.8 F g −1 for the mass of MnO 2 at a current density of 2 A g −1 ), a high capacitance retention of 61.8% even at a high current density of 50 A g −1 , and an excellent cycling stability of 89.6% capability retention after 5000 cycles. These findings offer a simple and environmentally friendly strategy for preparing advanced energy materials by utilizing the unique structure of biomass waste from nature. [ABSTRACT FROM AUTHOR]

In this paper, we prepared three different kinds of hollow activated carbon fibers (HACFs) from willow catkins (WCs), phenolic- and pitch-based hollow fibers, respectively. The morphology, pore structure, surface chemical composition and electrochemical properties of these hollow fibers were studied in parallel. Due to its high-hollow, cost-effective as well as eco-friendly nature, HACFs derived from WCs can be served as excellent electrode materials for electrochemical energy storage devices. Electrochemical measurements illustrate that the WCs derived HACFs exhibit not only high specific capacitance of 333 F g −1 at 0.1 A g −1 but also considerable rate capability with a retention of 62.7% (209 F g −1 at 10 A g −1 ). Symmetric supercapacitor devices that using WCs derived HACFs as electrodes deliver a maximum energy density of ∼8.8 Wh kg −1 at power density of 50 W kg −1 and good cycling performance with 95.5% retention over 3000 cycles at 5 A g −1 in 6 M KOH aqueous electrolytes. [ABSTRACT FROM AUTHOR]

A novel bio-inspired hollow activated carbon microtubes (HACMs) was prepared from low-cost, renewable biomass willow catkins by low temperature pre-carbonization combined with KOH chemical activation and used as supercapacitor electrode materials. The as-prepared HACMs exhibit hollow fiber-like structure with thin wall thickness of less than 1 µm, high microporosity surface area (997 m 2 g −1 ) and concentrated pore size distribution (1–2 nm). The electrochemical measurement results demonstrate that the HACMs electrode materials have high gravimetric capacitance of 306 F g −1 superior to most of the previously reported activated carbons and outstanding volumetric capacitance of 303 F cm −3 . [ABSTRACT FROM AUTHOR]

• Composites with Co@C nanoparticles anchored on porous carbon fibers are synthesized. • Annealing temperature has great effect on electromagnetic properties. • Sample annealing at 700 ℃ exhibits excellent microwave absorption performance. • Effective absorption bandwidth of 5.44 GHz is obtained at thickness of 1.7 mm. • Excellent absorption ascribed to moderate attenuation ability and better impedance matching. In this work, a self-polymerization route was adopted to construct willow catkins/Co-based metal–organic frameworks, which was followed by subsequent sintering to fabricate composites with Co/C nanoparticles anchored on porous carbon fibers. The annealing temperature for the composites had a significant influence on the tuning of the chemical composition, micromorphology, and absorption performance. The sample annealing at 700℃ exhibited excellent microwave absorption performance, in which the effective absorption bandwidth (reflection loss ≤−10 dB) was up to 5.44 GHz with a thickness of 1.7 mm and filling content of 25 wt%. The key factor for realizing excellent absorption was ascribed to its moderate microwave attenuation ability and better impedance matching. This work could contribute to the design of novel biomass-derived microwave absorption materials with low thickness, large bandwidth, and lightweight. [ABSTRACT FROM AUTHOR]

Unusual sheets-like primary activated carbon particles interconnected into three-dimensional micrometer-level large pores were prepared from a novel biomass named willow catkins (WCs) by KOH chemical activation process and used as electrode materials for supercapacitors. The pore structures, surface area and chemical properties could be facilely adjusted by changing the activation temperature. When the activation temperature increased from 600 to 800 °C, the specific surface area of the porous carbon product increased remarkably while the contents of nitrogen and oxygen co-doped decreased, which significantly affected the electrochemical properties of the porous carbon-based supercapacitors. The activated carbons from 600 °C activation possesses despite moderate specific surface area (645 m 2 g −1 ), concentrated pore size distribution of 0.77 nm, but high nitrogen (2.51 wt.%) and oxygen (13.28 wt.%) contents, high graphitization degree as well as good electrical conductivity. The supercapacitors with the carbon electrode reached maximal specific capacitances of 340 F g −1 and high specific surface capacitance of 52.7 μF cm −2 at the current density of 0.1 A g −1 , good rate capability (231 F g −1 at 10 A g −1 ) and good cycling stability (92% capacitance retention over 3000 cycles). The favorable capacitive performances make the waste biomass WCs act as a new resource of carbonaceous materials for high performance supercapacitors. [ABSTRACT FROM AUTHOR]

• A simple and low-cost strategy to prepare hierarchical carbon microtubes (CT). • The CT derived from willow catkins is first applied in a cathode for Li–S battery. • The percentage content of S element CT/S composite achieves a value of 75%. • Low degradation rate (0.13%) have been achieved with S mass loading = 2.6 mg/cm2. It is crucial but quite challenging to cycle carbon waste to prepare useful carbon material for energy storage by green process. Herein, hierarchical porous carbon microtubes synthesized by directly heating willow catkins without activation were used for Li–S batteries. The carbon microtubes loaded >75.0% sulfur were used as the Li–S battery cathodes. The cathodes with high areal sulfur content of 2.6 mg/cm2 deliver an initial discharge capacity of ~800 mAh/g at 0.5 C, and stabilized at 624 mAh/g after ~150 cycles at 0.5 C, with a low degradation rate per cycle (0.13% after 150 cycles or 0.07% after 1000 cycles). Our investigation presents that the fly willow catkins air-contaminants could be collected to use for high-density energy storage. [ABSTRACT FROM AUTHOR]