Surface group modification and functionalization of two-dimensional materials in many cases are deemed as effective approaches to achieve some distinctive properties. Herein, we present a new nanoflower-shaped TiO2/C composite which was synthesized by in situ alcoholysis of two-dimensional layered MXene (Ti3C2(OHxF1–x)2) in a dilute HF solution (0.5 wt %) for the first time. Furthermore, it is demonstrated that it bestows a strong catalytic activity for the dehydrogenation of NaAlH4. The results show that the NaAlH4 containing 10 wt % A0.9R0.1–TiO2/C (containing 90% anatase TiO2 and 10% rutile TiO2) composite merely took ∼85 min to reach a stable and maximum dehydrogenation capacity of ∼3.08 wt % at 100 °C, and it maintains stable after ten cycles, which is the best Ti-based catalyst for the dehydrogenation of NaAlH4 reported so far. Theoretical calculation confirms that this C-doping TiO2 crystals remarkably decreases desorption energy barrier of Al–H bonding in NaAlH4, accelerating the breakdown of Al–H bonding. This finding raises the potential for development and application of new fuel cells.Keywords: catalytic properties; dehydrogenation; MXene; phase transformation; two dimension;

Differing from graphene, the activated groups on the surface of layered two-dimensional titanium carbide (MXene) materials bestow superiority to self-assemble some novel MXene derivatives with intriguing chemical/physical properties. Here we first report a series of new MXene-Ag composites by directly mixing AgNO3 and alkalization-intercalated MXene (alk-MXene, Ti3C2(OH/ONa)2) solution containing polyvinylpyrrolidone (PVP) at room temperature, in which an analogous urchin-shaped MXene-Ag0.9Ti0.1 bimetallic nanowire composite exhibits unexpected electrocatalytic activity for the oxygen reduction reaction. The addition of PVP solution induces the formation of 5-fold nanotwin Ag seeds, which then grow into Ag/Ti (Ag0.9Ti0.1) bimetallic nanowires. The unique bimetallic nanowires favor a four-electron transfer process, and exhibit high current density and good stability by offering numerous oxygen adsorption sites and shortening the diffusion path of adsorbed oxygen. The results represent a new step for the electrocatalytic applications of MXene materials, and also motivate enthusiasm in the quest for new MXene derivations.Keywords: Bimetal; MXene; Nanowires; Oxygen reduction reaction;

•A simple method to prepare a new C-N/Ag-K hybrid, which offer good ORR catalytic activity.•The comprehensive catalytic properties are near to the commercial Pt/C.•The sample activated with KOH has high BET aera.•The sample C-N/Ag-900-K shows the good property in Zn-air battery.A novel nitrogen-doped biomass carbon/silver (C-N/Ag) composite has been synthesized by a simple method, wherein the precursor of soymilk simultaneously serves as carbon and nitrogen sources, reductant and substrate. The structure, morphology and valence state of samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectra. Results show the formation of nano-sized Ag homogenously disperses on the surface of mesoporous substrate, and the self-reduction role mainly attributes to the presence of unsaturated carbon bonding. Electrochemical properties were characterized by galvanostatic discharge and impedance spectra techniques. The sample prepared with 1 mmol AgNO3 solution, activated by 0.1 M KOH and annealed at 900 °C shows excellent oxygen reduction reaction activity and good electrochemical durability in alkaline medium. The onset potential, limiting diffusion current density and electron transfer number are 0.93 V, 6.26 mA cm−2 and 4.00, respectively, superior to those of 60 wt.% Ag/C and comparable to 20 wt.% Pt/C catalysts correspondingly. The discharge performance of Zn-air batteries is better than that of 20 wt% Pt/C.

•The “rod-like” biomass-based nano-La(III) (hydr)oxides was newly prepared.•Ws-N-La shows higher preference towards phosphate than commercial HFO-201.•The “needle-like” LaPO4·xH2O is formed during phosphate adsorption.•No obvious capacity loss was observed after 10th regeneration.Enhanced removal of phosphate by biomass-supported adsorbents is an effective and economic method to prevent the accelerated eutrophication in water body. A new nanocomposite Ws-N-La is fabricated for efficient phosphate removal by immobilizing “rod-like” nano-sized La(III) (hydr)oxides within a quaternary-aminated wheat straw (Ws-N). It exhibits higher adsorption capacity towards phosphate than the commercial IRA-900 or HFO-201 even at higher competing anions levels. The pH result indicated that the Ws-N-La would effectively sequestrate phosphate over a wide pH range between 3.0 and 7.0 without significant La(III) leaching. Ten cycles of adsorption-desorption experiments reveals that no significant capacity loss is observed, indicating excellent stability and repeated use property than any other La(III)-based adsorbents. The results of TEM, XRD and XPS analysis demonstrated that the formation of “needle-like” lanthanum phosphate nanoparticle is the dominant pathway for the specific adsorption of phosphate by nano-La(III) (hydr)oxides. All the results suggested that the biomass-supported nano-composite Ws-N-La can serve as a promising adsorbent for preferable phosphate removal in realistic application.Advanced removal of phosphate by low-cost nano-composite with excellent adsorption selectivity and regeneration ability.Download high-res image (236KB)Download full-size image

A new MXene/Ag composite was synthesized by direct reduction of a AgNO3 aqueous solution in the presence of MXene (Ti3C2(OH)0.8F1.2). The as-received MXene/Ag composite can be deemed as an excellent anode material for lithium-ion batteries, exhibiting an extraordinary long cycle lifetime with a large capacity at high charge–discharge rates. The results show that Ag self-reduction in MXene solution is related to the existence of low-valence Ti. Reversible capacities of 310 mAh·g–1 at 1 C (theoretical value being ∼320 mAh·g–1), 260 mAh·g–1 at 10 C, and 150 mAh·g–1 at 50 C were achieved. Remarkably, the composite withstands more than 5000 cycles without capacity decay at 1–50 C. The main reasons for the long cycle life with high capacity are relevant to the reduced interface resistance and the occurrence of Ti(II) to Ti(III) during the cycle process.Keywords: composite; lithium batteries; MXene; self-reduction

•The Pb removal ability of all M2X (OH) MXene was investigated by first principles.•The most attractive MXene material was obtained.•The Pb removal difference between transition metals, C and N were studied.The alkalization-intercalated MXene (Alk-MXene: Ti3C2(OH)2) has recently confirmed as a new and effective material for removing Pb heavy metal. Herein, taking into account of the complexity and diversity of MXenes, the Pb adsorption behavior of different MXenes with the highest valuable applied structure of M2X (OH)2 (M = Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and X = C or N) has been systemically investigated by first principles calculations utilizing the generalized gradient approximation with the density functional theory, which paves a desirable trajectory for the applications of MXenes. Basically, the formation energies of M2N(O2H2−2xPbx) are lower than those of M2C(O2H2−2xPbx), suggesting the substitution of N is more effective for the Pb adsorption in contrast to C due to the different valence electron numbers between C and N atoms. In addition, the results show that the Ti2C(OH)2 is the most favorite one for the lowest mass fraction to lead removal. Notably, both Sc2C(OH)2 and Zr2C(OH)2 structures don’t have the ability of Pb removal. The kinetics of the lead removal was elucidated on the variation of potential wells by virtue of the density of states and electron localization function.

In this study, the hydrogel materials of reduced graphene oxide (RGO)/chitosan/silver nanoparticle composites were designed and prepared via a self-assembly process and simultaneous reduction of chitosan molecules with GO. These as-prepared hydrogels were characterized by different techniques. The morphology of the internal network structure of the nanocomposite hydrogels was investigated. The catalytic capacity results demonstrate that the prepared GO-based composite hydrogels can efficiently remove two tested dye molecules from wastewater in good accordance with the pseudo-second-order model. The dye photocatalytic capacity of the obtained hydrogels is mainly attributed to the silver nanoparticle on RGO sheets, whereas the chitosan molecule was incorporated to facilitate the gelation process of the GO sheets. Interestingly, the as-prepared catalytic composite material serves as a good photocatalyst for two presently used dyes even for dye mixtures, suggesting the potentially real applications of the GO composite materials for wastewater treatment as well as the removal of harmful dyes.Keywords: Chitosan; Composite hydrogel; Dye degradation; Graphene oxide; Wastewater treatment

Artemia nauplii are important bait or food sources in aquaculture, but the egg shells after incubation are always subjected to discarding as natural wastes; therefore, application and utilization of the Artemia egg-shell wastes will be an important issue. Herein, we reported a new hybrid biomaterial by encapsulating nano-Mg(OH)2 onto discarded Artemia egg shells for phosphate sequestration enhancement. The unique hierarchically 3D-layered structure of Artemia egg shells can endow well-defined nano-Mg(OH)2 morphology and efficient phosphate adsorption performances. The results of the final hybrid biomaterial exhibit a wide pH dependent sorption process, strong affinity toward phosphate removal, and large sorption capacity. Moreover, the exhausted adsorbent shell–Mg-P can be further utilized as slow-release fertilizer without regular chemical regeneration. The efficient slow-release behaviors of phosphorus onto Shell–Mg–P for 30 days indicated the potential applicability as fertilizers. Additionally, the actual seedling tests further confirm that the shell–Mg–P can be readily used as a slow-release fertilizer for the soil improvement and crop productivity.Keywords: Artemia egg shell; Biomaterial; Plant grown; Waste;

Phosphate is a worldwide environmental issue, due to possibly causing serious eutrophication and subsequently blue-green algae blooms. Sequestrating phosphate by exploitation of advanced materials with a hierarchical morphology will be an important pathway. Herein, we fabricated a new sea urchin-like zirconium(IV) oxide (Ur-Zr) using a one step facile alcoholysis solvothermal reaction for efficient phosphate removal. The as-obtained material exhibits adsorption properties in a wide range of pH conditions with the optimal pH ranging from 1.0 to 6.0; competition results reveal that the Ur-Zr displays remarkable sorption selectivity for phosphate removal with coexisting common anions (SO42−, NO3− and Cl− ions) at high concentrations, which can be ascribed to the unique hierarchical morphology and strong sorption affinity between Zr–O and phosphate species. Besides, the resultant Ur-Zr also shows a gradual sorption kinetics behavior, which can be well described by the pseudo-first-order model with the maximum sorption capacity of 74.8 mg g−1. Additionally, the exhausted materials can be recycled by alkaline treatment and used repeatedly. All of the results demonstrate that the sea urchin-like zirconium(IV) oxide is a competent candidate for enhanced phosphate removal.

Graphene oxide (GO)-chitosan composite hydrogels were successfully prepared via the self-assembly of chitosan molecules and GO. These as-prepared hydrogels were characterized by different techniques. The morphology of the internal network structure of the nanocomposite hydrogels was investigated. The adsorption capacity results demonstrate that the prepared GObased composite hydrogels can efficiently remove three tested dye molecules, Congo red, methylene blue and Rhodamine B, from wastewater in accordance with the pseudo-second-order model. The dye adsorption capacity of the obtained hydrogels is mainly attributed to the GO sheets, whereas the chitosan molecule was incorporated to facilitate the gelation process of the GO sheets. The present study indicates that the as-prepared composite hydrogels can serve as good adsorbents for wastewater treatment as well as the removal of harmful dyes.本文通过壳聚糖分子与氧化石墨烯(GO)的自组装成功制备了GO-壳聚糖复合水凝胶, 并对该水凝胶进行了表征. 研究发现复合水凝胶中存在网状微观结构. 吸附性能结果表明制得的基于GO的复合水凝胶可以有效地从废水中去除三种测试染料分子, 同时符合准二阶模型. 该水凝胶的染料吸附能力主要来源于GO片层, 而壳聚糖分子促进了GO片层的凝胶化过程. 目前的研究结果表明制备的复合水凝胶可以作为良好的吸附剂应用于废水处理以及有害染料去除等领域.

The two-dimensional (2D) layered MXene (Ti3C2(OH)xF2–x) material can be alkalization intercalated to achieve heavy-metal ion adsorption. Herein the adsorption kinetics of heavy-metal ions and the effect of intercalated sites on adsorption have been interpreted by first-principles with density functional theory. When the coverage of the heavy-metal ion is larger than 1/9 monolayer, the two-dimensional alkalization-intercalated MXene (alk-MXene: Ti3C2(OH)2) exhibits strong heavy-metal ion absorbability. The hydrogen atoms around the adsorbed heavy-metal atom are prone to form a hydrogen potential trap, maintaining charge equilibrium. In addition, the ion adsorption efficiency of alk-MXene decreases due to the occupation of the F atom but accelerates by the intercalation of Li, Na, and K atoms. More importantly, the hydroxyl site vertical to the titanium atom shows a stronger trend of removing the metal ion than other positions.

The functional groups and site interactions on the surfaces of two-dimensional (2D) layered titanium carbide can be tailored to attain some extraordinary physical properties. Herein a 2D alk-MXene (Ti3C2(OH/ONa)xF2–x) material, prepared by chemical exfoliation followed by alkalization intercalation, exhibits preferential Pb(II) sorption behavior when competing cations (Ca(II)/Mg(II)) coexisted at high levels. Kinetic tests show that the sorption equilibrium is achieved in as short a time as 120 s. Attractively, the alk-MXene presents efficient Pb(II) uptake performance with the applied sorption capacities of 4500 kg water per alk-MXene, and the effluent Pb(II) contents are below the drinking water standard recommended by the World Health Organization (10 μg/L). Experimental and computational studies suggest that the sorption behavior is related to the hydroxyl groups in activated Ti sites, where Pb(II) ion exchange is facilitated by the formation of a hexagonal potential trap.

•New binary organogels in single or mixed solvents were prepared.•Various nanostructures and hydrogen bonds from different solvents were investigated.•Solvents and molecular skeletons are crucial to the gelation behaviors.•Suitable single/volume ratios in mixed solvents are favorable for gel formation.In this paper new binary organogels based on glutamic acid derivatives and acids with different molecular skeletons were designed and prepared. Their gelation behaviors in single or mixed solvents were tested as novel low-molecular-mass organic gelators. The experimental data showed that the solvents and molecular skeletons played a crucial role in regulating the gelation behaviors and fabrication of nanostructures. Suitable single solvents or volume ratios in ethanol/water mixed solvents seemed more favorable for the formation of supramolecular gels due to cooperation of multi-intermolecular weak forces. Rational assembly modes in organogels were proposed and discussed. The present work may give some insight to design and character new versatile organogelators and soft materials with special molecular structures.