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An iron-coordinated covalent triazine polymer-derived Fe–Nx nanoparticle-embedded nitrogen-doped carbon nanofloret composite is successfully designed by Liu and co-workers. Thanks to its abundant Fe–Nx nanoparticles active centers and large specific surface area, the optimal Fe/N@-CNF-800 can readily work as an efficient pH-universal electrochemical oxygen reduction catalyst for a high-performance zinc-air battery. (Yong Zheng, Mingjin Li, Yongye Wang, Niu Huang, Wei Liu, Sha [Detail] ...
As promising electrode materials for supercapacitors, nickel-cobalt bimetallic sulfides render the advantages of abundant redox reactions and inherently high conductivity. However, in general, unsatisfactory performance of low specific capacity, low rate capability, and fast capacity loss exist in Ni–Co sulfide electrodes. Herein, we rationally regulate phosphorus-doped nickel–cobalt sulfides (P-NCS) to enhance the electrochemical performance by gas–solid phosphorization. Moreover, carbon nanotubes (CNTs) as conductive additives are added to improve the cycle stability and conductivity and form the composite P-NCS/C/CNT. According to density functional theory, more electrons near the Fermi surface of P-NCS are demonstrated notionally than those of simple CoNi2S4. Electrochemical results manifest that P-NCS/C/CNT exhibits superior electrochemical performance, e.g., high specific capacity (932.0 C∙g‒1 at 1 A∙g‒1), remarkable rate capability (capacity retention ratio of 69.1% at 20 A∙g‒1), and lower charge transfer resistance. More importantly, the flexible hybrid asymmetric supercapacitor is assembled using P-NCS/C/CNT and activated carbon, which renders an energy density of 34.875 W·h∙kg‒1 at a power density of 375 W∙kg‒1. These results show that as-prepared P-NCS/C/CNT demonstrates incredible possibility as a battery-type electrode for high-performance supercapacitors.
Phenolic resins were employed to prepare electrospun porous carbon nanofibers with a high specific surface area as free-standing electrodes for high-performance supercapacitors. However, the sustainable development of conventional phenolic resin has been challenged by petroleum-based phenol and formaldehyde. Lignin with abundant phenolic hydroxyl groups is the main non-petroleum resource that can provide renewable aromatic compounds. Hence, lignin, phenol, and furfural were used to synthesize bio-based phenolic resins, and the activated carbon nanofibers were obtained by electrospinning and one-step carbonization activation. Fourier transform infrared and differential scanning calorimetry were used to characterize the structural and thermal properties. The results reveal that the apparent activation energy of the curing reaction is 89.21 kJ·mol–1 and the reaction order is 0.78. The activated carbon nanofibers show a uniform diameter, specific surface area up to 1100 m2·g–1, and total pore volume of 0.62 cm3·g–1. The electrode demonstrates a specific capacitance of 238 F·g–1 (0.1 A·g–1) and good rate capability. The symmetric supercapacitor yields a high energy density of 26.39 W·h·kg–1 at 100 W·kg–1 and an excellent capacitance retention of 98% after 10000 cycles. These results confirm that the activated carbon nanofiber from bio-based phenolic resins can be applied as electrode material for high-performance supercapacitors.
All-inorganic cesium lead bromide (CsPbBr3) perovskite solar cells have been attracting growing interest due to superior performance stability and low cost. However, low light absorbance and large charge recombination at TiO2/CsPbBr3 interface or within CsPbBr3 film still prevent further performance improvement. Herein, we report devices with high power conversion efficiency (9.16%) by introducing graphene oxide quantum dots (GOQDs) between TiO2 and perovskite layers. The recombination of interfacial radiation can be effectively restrained due to enhanced charge transfer capability. GOQDs with C-rich active sites can involve in crystallization and fill within the CsPbBr3 perovskite film as functional semiconductor additives. This work provides a promising strategy to optimize the crystallization process and boost charge extraction at the surface/interface optoelectronic properties of perovskites for high efficient and low-cost solar cells.
Fe–Nx nanoparticles-embedded porous carbons with a desirable superstructure have attracted immense attention as promising catalysts for electrochemical oxygen reduction reaction. Herein, we employed Fe-coordinated covalent triazine polymer for the fabrication of Fe–Nx nanoparticle-embedded porous carbon nanoflorets (Fe/N@CNFs) employing a hypersaline-confinement-conversion strategy. Presence of tailored N types within the covalent triazine polymer interwork in high proportions contributes to the generation of Fe/N coordination and subsequent Fe–Nx nanoparticles. Owing to the utilization of NaCl crystals, the resultant Fe/N@CNF-800 which was generated by pyrolysis at 800 °C showed nanoflower structure and large specific surface area, which remarkably suppressed the agglomeration of high catalytic active sites. As expect, the Fe/N@CNF-800 exhibited unexpected oxygen reduction reaction catalytic performance with an ultrahigh half-wave potential (0.89 V vs. reversible hydrogen electrode), a dominant 4e– transfer approach and great cycle stability (> 92% after 100000 s). As a demonstration, the Fe/N-PCNF-800-assembled zinc–air battery delivered a high open circuit voltage of 1.51 V, a maximum peak power density of 164 mW·cm–2, as well as eminent rate performance, surpassing those of commercial Pt/C. This contribution offers a valuable avenue to exploit efficient metal nanoparticles-based carbon catalysts towards energy-related electrocatalytic reactions and beyond.
The past decade has witnessed a variety of members of the carbon family along with exposure of carbon dots due to their magnificent properties in sensing, bioimaging, catalytic applications, biomedical fields, and so on. Herein, we report the simple hydrothermal method to fabricate photoluminescent doped carbon quantum dots for the detection of noxious lead(II) ions. Lead(II) ion is very venomous for both the environment and human health for which its detection is demanded area in the research field. The as-prepared carbon dots show excellent photostability, low toxicity and significant photoluminescence properties along with good water solubility. Along with these properties, carbon dots have a quantum yield of approximately 15%. In the practical field of application, these carbon dots have been used as sensing probes for the detection of lead(II) ions with a detection limit of 60 nmol·L–1. The fluorescence intensity of carbon dots was remarkably quenched in the presence of the lead(II) ion selectively among all the tested metal ions. Furthermore, we have studied the Stern–Volmer relationship for lead(II) quenching along with the explanation of the probable quenching mechanism. Ability of the doped carbon dots in heavy metal ions sensing in an environmental sample was demonstrated.
Covalent organic frameworks (COFs) have been increasingly used in capillary electrochromatography due to their excellent characteristics. In this work, hydrazine-linked TFPB-DHzDS (TFPB: 1,3,5-tris(4-formylphenyl)benzene; DHzDS: 2,5-bis(3-(ethylthio)propoxy)terephthalohydrazide) was first synthesized by a simpler and easier method at room temperature and introduced into capillary electrochromatography as coating material. The TFPB-DHzDS coated capillaries were prepared by an in-situ growth process at room temperature. After optimizing the coating concentration and experimental conditions of capillary electrochromatography, baseline separation of two groups of polycyclic aromatic hydrocarbons was achieved based on the TFPB-DHzDS coated capillary. And the established method was used successfully to determine PAHs in natural water and soil samples. The spiked recoveries of polycyclic aromatic hydrocarbons in these samples ranged from 90.01% to 111.0%, indicating that the method is reliable and could detect polycyclic aromatic hydrocarbons in natural samples. Finally, molecular simulation was applied to study and visualize the interaction between the analytes and coating COF materials to investigate the molecular level separation mechanism further.
Indium tin oxide films, an important n-type semiconductor oxide, show great prospects in optoelectronic device applications. Consequently, as a key raw material of targets for sputtering films, it is important to prepare low-resistivity indium tin oxide powders. Herein, low-resistivity indium tin oxide submicro-cubes are synthesized by a seed-assisted coprecipitation method. The effects of seed content, In3+ concentration, aging time, reaction temperature and calcination temperature on resistivity were investigated by single factor and orthogonal experiments. To ensure reliability and reproducibility of data, each experiment was repeated three times and resistivity of each sample was measured three times to obtain average value. The results indicated that optimal sample was matched with cubic phase In2O3. The single-crystal indium tin oxide particles exhibited a regular cubic shape with a size of nearly 500 nm and low resistivity of 0.814 Ω·cm. Compared with particles prepared by the conventional coprecipitation method, indium tin oxide submicro-cubes showed good dispersion. The presence of seed particles provided nucleation sites with lower energy barriers and promoted formation of submicro-cubes. The face-to-face contact among particles and good dispersion contributed to electron transfer, resulting in lower resistivity. The seed-assisted synthesis provides a novel way to prepare low-resistivity indium tin oxide submicro-cubes.
Recently, metal–organic frameworks are one of the potential catalytic materials for electrocatalytic applications. The oxygen reduction reaction and oxygen evolution reaction catalytic activities of heterometallic cluster-based organic frameworks are investigated using density functional theory. Firstly, the catalytic activities of heterometallic clusters are investigated. Among all heterometallic clusters, Fe2Mn–Mn has a minimum overpotential of 0.35 V for oxygen reduction reaction, and Fe2Co–Co possesses the smallest overpotential of 0.32 V for oxygen evolution reaction, respectively 100 and 50 mV lower than those of Pt(111) and RuO2(110) catalysts. The analysis of the potential gap of Fe2M clusters indicates that Fe2Mn, Fe2Co, and Fe2Ni clusters possess good bifunctional catalytic activity. Additionally, the catalytic activity of Fe2Mn and Fe2Co connected through 3,3′,5,5′-azobenzenetetracarboxylate linker to form Fe2M–PCN–Fe2M is explored. Compared with Fe2Mn–PCN–Fe2Mn, Fe2Co–PCN–Fe2Co, and isolated Fe2M clusters, the mixed-metal Fe2Co–PCN–Fe2Mn possesses excellent bifunctional catalytic activity, and the values of potential gap on the Mn and Co sites of Fe2Co–PCN–Fe2Mn are 0.69 and 0.70 V, respectively. Furthermore, the analysis of the electron structure indicates that constructing a mixed-metal cluster can efficiently enhance the electronic properties of the catalyst. In conclusion, the mixed-metal cluster strategy provides a new approach to further design and synthesize high-efficiency bifunctional electrocatalysts.
Selective separation of dissolved tungsten and vanadium is of great significance for the utilization of the secondary resources of these elements. In this work, selective removal of vanadium from tungstate solutions via microbubble floating-extraction was systematically investigated. The results indicated that vanadium can be more easily mineralized over tungsten from tungstate solutions using methyl trioctyl ammonium chloride as mineralization reagent under weak alkaline conditions. Owing to the higher bubble and interface mass transfer rates, high-efficiency enrichment and deep separation of vanadium could be achieved easily. Additionally, the deep recovery of tungsten and vanadium from the floated organic phase could be easily realized using a mixed solution of sodium hydroxide and sodium chloride as stripping agents. The separation mechanism mainly included the formation of hydrophobic complexes, their attachment on the surface of rising bubbles, and their mass transfer at the oil–water interface. Under the optimal conditions, the removal efficiency of vanadium reached 98.5% with tungsten loss below 8% after two-stage microbubble floating-extraction. Therefore, the microbubble floating-extraction could be an efficient approach for separating selectively vanadium from tungstate solutions, exhibiting outstanding advantages of high separation efficiency and low consumption of organic solvents.
The increasing amount of food waste from various industrial, agricultural, and household sources is an environmental burden if managed inappropriately. Numerous waste management approaches have been developed for the disposal of food waste, but still suffer from either high cost, production of toxic by-products, or secondary environmental pollutions. Herein, we report a new and sustainable plasma electrolysis biorefinery route for the rapid and efficient liquefaction of food waste. During the plasma electrolysis process, only the solvent is added to liquefy the waste, and anions in the waste can contribute to catalyzing the biowaste conversion. While liquefying the waste, the highly reactive species produced in the plasma electrolysis process can efficiently reduce the content of O, N, and Cl in the liquefied products and oxidize most of the metals into solid residues. Especially, the removal rate of Na and K elements was greater than 81%, which is significantly higher than using the traditional oil bath liquefaction, resulting in a relatively high-quality biocrude oil with a high heating value of 25.86 MJ·kg–1. Overall, this proposed strategy may provide a new sustainable and eco-friendly avenue for the power-to-chemicals valorization of food waste under benign conditions.
In this study, the hydrogen evolution performance of CdS nanorods is improved using ZnCo2O4. ZnCo2O4 nanospheres are synthesized using the hydrothermal and calcination methods, and CdS nanorods are synthesized using the solvothermal method. From the perspective of morphology, numerous CdS nanorods are anchored on the ZnCo2O4 microspheres. According to the experimental results of photocatalytic hydrogen evolution, the final hydrogen evolution capacity of 7417.5 μmol∙g–1∙h–1 is slightly more than two times that of the single CdS, which proves the feasibility of our study. Through various characterization methods, it is proved that the composite sample has suitable optoelectronic properties. In addition, ZnCo2O4 itself exhibits good conductivity and low impedance, which shortens the charge-transfer path. Overall, the introduction of ZnCo2O4 expands the adsorption range of light and improves the performance of photocatalytic hydrogen evolution. This design can provide reference for developing high-efficiency photocatalysts.
MnOx and Sm–Mn catalysts were prepared with the coprecipitation method, and they showed excellent activities and sulfur resistances for the selective catalytic reduction of NOx by NH3 between 50 and 300 °C in the presence of excess oxygen. 0.10Sm–Mn catalyst indicated better catalytic activity and sulfur resistance. Additionally, the Sm doping led to multi-aspect impacts on the phases, morphology structures, gas adsorption, reactions process, and specific surface areas. Therefore, it significantly enhances the NO conversion, N2 selectivity, and sulfur resistance. Based on various experimental characterization results, the reaction mechanism of catalysts and the effect of SO2 on the reaction process about the catalysts were extensively explored. For 0.10Sm–Mn catalyst, manganese sulfate and sulfur ammonium cannot be generated broadly under the influence of SO2 and the amount of surface adsorbed oxygen. The Bronsted acid sites strengthen significantly due to the addition of SO2, enhancing the sulfur resistance of the 0.10Sm–Mn catalyst.
