Latest ArticlesMorphology-controlled electrocatalysts with the ability of CO2 adsorption/activation, mass transfer, high stability and porosity are much desired in electrochemical CO2 reduction reaction (CO2RR). Here, three kinds of multi-dimensional nanostructures (i.e., hollow sphere, nanosheets and nanofibers) have been successfully produced through the modulation of porphyrin-based covalent organic frameworks (COFs) with various modulators. The obtained nanostructures with high-stability, large surface-area, and single metal sites enable efficient CO2RR into CH4. Notably, they all exhibit higher FE (hollow sphere, 68.2%; nanosheet, 64.2% and nanofiber, 71.0%, −0.9 V) than COF-366-Cu (43.0%, −0.9 V) after morphology control. Noteworthy, the FE of COF-366-Cu (HS) keeps higher than 52.4% over a wide potential range from −0.9 V to −1.1 V and the achieved FECH4+C2H4 (82.8%, −0.9 V) is superior to most of reported COFs and copper-based electrocatalysts. This work paves a new way in the exploration of COF-based multi-dimensional nanostructures applicable in efficient CO2RR to CH4.
2D transition metal dichalcogenides (TMDCs) have drawn an enormous amount of attention due to their fascinating properties and application potential in next-generation information process and storage. However, the lack of proper synthesis approach limits their application. Here, we report a controllable synthesis method to grow ultrathin MS2 (M = Ti, Nb, Zr) nanosheets with H2S-assisted chemical vapor deposition (CVD). We found that the presence of H2S plays an important role to control the morphology of nanosheets including the lateral size and the nucleation density. With the assistance of H2S, the growth of MS2 shows much thinner thickness with largely decreased nucleation density, beneficial for the device application, which can be attributed to the kinetics dominated growth. Our method hence opens a new avenue for the CVD growth of 2D TMDCs and the corresponding heterojunction, and paves the way for exploring their intriguing properties and applications.
In recent years, especially when there is increasing concern about the safety issue of lithium-ion batteries (LIBs), aqueous Zn-ion batteries (ZIBs) have been getting a lot of attention because of their cost-effectiveness, materials abundance, high safety, and ecological friendliness. Their working voltage and specific capacity are mainly determined by their cathode materials. Vanadium oxides are promising cathode materials for aqueous ZIBs owing to their low cost, abundant resources, and multivalence. However, vanadium oxide cathodes still suffer from unsatisfactory capacity, poor stability, and low electrical conductivity. In this work, cascading V2O3/nitrogen doped carbon (V2O3/NC) hybrid nanosheets are prepared for high-performance aqueous ZIBs by pyrolyzing pentyl viologen dibromide (PV) intercalated V2O5 nanosheets. The unique structure features of V2O3/NC nanosheets, including thin sheet-like morphology, small crystalline V2O3 nanoparticles, and conductive NC layers, endow V2O3/NC with superior performance compared to most of the reported vanadium oxide cathode materials for aqueous ZIBs. The V2O3/NC cathode exhibits the discharge capacity of 405 mAh/g at 0.5 A/g, excellent rate capability (159 mAh/g at 20 A/g), and outstanding cycling stability with 90% capacity retention over 4000 cycles at 20 A/g.
Deuteration of hydrogen-bonded phase transition crystals can increase the transition temperatures due to the isotope effect. But rare examples show the opposite trend that originates from the structural changes of the hydrogen bond, known as the geometric H/D isotope effect. Herein, we report an organic crystal, diethylammonium hydrogen 1,4-terephthalate, exhibits a reversible structural phase transition and dielectric switching. Structural study shows the cations reside in channels formed by one-dimensional hydrogen-bonded anionic chains and undergo an order-disorder transition at around 206 K. The deuterated counterpart shows an elongation of the O···O hydrogen bond by about 0.005 Å. This geometric isotope effect releases the internal pressure of the anionic host on the cation guests and results in a downward shift of the phase transition temperature by 10 K.
The effects of two solid-based hydrogen peroxides sodium percarbonate (SPC) and calcium peroxide (CP) on waste activated sludge (WAS) disintegration were investigated. Both oxidants achieved efficient WAS disintegration for the synergistic effect of alkaline and oxidation. The strong alkaline condition led to the leakage of ammonia and the existence of abundant calcium ions accelerated the fixation of phosphorus via precipitation in CP WAS disintegration process. However, the spongy-like layer and low pH condition retarded the release of gaseous ammonia in SPC group. Hydroxyl radical was the main oxygen reactive species in SPC approaches which were more intense than CP by electron spin resonance (ESR) analysis. CP treated WAS contented more small particle size matter and total suspended solids (TSS) increased dramatically. In conclusion, CP pretreated sludge was more suitable for fertilization, while SPC was in favor of anaerobic digestion. This study clarified the differences between these two oxidants and their intermediates on nutrients release in sludge disintegration.
Hydrogen energy (H2) has been considered as the most possible consummate candidates for replacing the traditional fossil fuels because of its higher combustion heat value and lower environmental pollution. Photocatalytic hydrogen evolution (PHE) from water splitting based on semiconductors is a promising technology towards converting solar energy into sustainable H2 fuel evolution. Developing high-activity and abundant source semiconductor materials is particularly important to realize highly efficient hydrogen evolution as for photocatalysis technology. However, unmodified pristine photocatalysts are often unable to overcome the weakness of low performance due to their limitations. In recent years, transition metal phosphides (TMPs) were used as valid co-catalysts to replace the classic precious metal materials in the process of photocatalytic reaction owing to their lower cost and higher combustion heat value. What is more, bimetallic phosphides have been also caused widespread concern in H2 evolution reaction owing to its much lower overpotential, more superior conductivity, and weaker charge carriers transfer impedance in comparison to those of single metal phosphides. In this minireview, we concluded the latest developments of bimetallic phosphides for a series of photocatalytic reactions. Firstly, we briefly summarize the present loading methods of bimetallic phosphides (BMPs) anchored on the photocatalyst. After that, the H2 evolution efficiency based on BMPs as cocatalyst is also studied in detail. Besides, the application of BMPs-based host photocatalyst for H2 evolution under dye sensitization effect has also been discussed. At last, the current development prospects and prospective challenges in many ways of BMPs are proposed. We sincerely hope this minireview has certain reference value for great developments of BMPs in the future research.
Developing all-solid-state polymer electrolytes (SPEs) with high electrochemical performances and stability is of great importance for exploiting of high energy density and safe batteries. Herein, ether linkage and imidazolium ionic liquid (ILs) are incorporated into the multi-armed polymer backbone though the series and parallel way. The parallel polymeric ionic liquid (P-P (PEGMA-IM)) maximizes the synergistic effect of ILs and ether linkage, which endowed the material with low crystallinity and high flame retardancy. The P-P (PEGMA-IM) based P-SPE presents a high ionic conductivity of 0.489 mS/cm at 60 ℃, an excellent lithium-ion transference number of 0.46 and a wide electrochemical window of 4.87 V. The assembled lithium metal battery using P-SPE can deliver a capacity of 151 mAh/g at 0.2 C, and the capacity retention ratio reaches 82% with a columbic efficiency beyond 99%. The overpotential of P-SPE based symmetric battery is 0.08 V, and there is no apparent magnifying even after 130 h cycling. This new design provides a new avenue for exploitation of advanced SPEs for the next-generation batteries.
Increasing active metal sites is a valid approach to improve the catalytic activity of the catalyst. Co3+ is the main active metal site of Co-based catalysts. In this research work, through the partial transformation of CoFePBA (CFP) via low-temperature heat treatment, the effective control of the Co3+/Co2+ ratio has been achieved. The partial transformation strategy of low-temperature heat treatment can not only maintain the original framework structure of CFP, but also increase more active sites. The characterization results show that the CFP-200 sample obtained via heat treatment at 200 ℃ for 2 h under N2 atmosphere has the highest Co3+/Co2+ ratio. As an oxygen evolution reaction electrocatalyst, CFP-200 shows the best electrocatalytic activity among all samples. In 1.0 mol/L KOH electrolyte, the overpotential is 312 mV at a current density of 10 mA/cm2. Therefore, low-temperature heat treatment provides an effective method for preparing low-cost and high-efficiency electrocatalysts.
Exploiting efficient and recyclable photocatalysts is a vital matter for environmental purification. Herein, cerium vanadate (CeVO4) sub-microspheres and silver nanowire (AgNW)@CeVO4 with core-shell architecture as photocatalysts are rationally constructed by hydrothermal approach. The AgNW@CeVO4 photocatalyst obtained by depositing CeVO4 on the surface of Ag NWs possess one dimensional continuous structure, which expand the optical absorption range and reduce the band gap of CeVO4 photocatalyst. Moreover, the resultant AgNW@CeVO4 photocatalyst demonstrates superior photocatalytic performance in the degradation of rhodamine B, methylene blue, and 4-nitrophenol pollutants upon solar light irradiation, compared with pure CeVO4. The excellent photocatalytic activity can be ascribed to the introduction of Ag NWs, which afford rapid charge transport channels and reservoir for the electrons in the AgNW@CeVO4 heterostructure to promote separation of electron–hole pairs. The first-principles investigations reveal increase of adsorption energy of oxygen molecules on the CeVO4 surface with the presence of Ag. Meanwhile, Ag NWs can further improve the photocatalytic efficiency of the AgNW@CeVO4 based on the plasmonic effect. More importantly, the good structural stability and recyclability of AgNW@CeVO4 are observed due to the strong synergistic effect, which ensures long-term usability of photocatalyst and great promise in water purification. This work can offer valuable reference into designs and construction of Ce-based heterojunction photocatalysts for environmental remediation.
Cell is the most basic unit of the morphological structure and life activity of an organism. Learning the composition, structure and function of cells, exploring the life activities of cells and studying the interaction between cells are of great significance for human cognition and control of the life activities of organisms. Therefore, rapid, convenient, inexpensive, high-precision and reliable methods of cell separation and analysis are being developed to obtain accurate information for the study of cytology and pathology. Microfluidic chip is a new emerging technology in recent years. It has a micromanufacturing structure, which can not only realize the precise space-time control of fluid and cells, but also reproduces the three-dimensional dynamic microenvironment of cell growth in the body. In addition, the microfluidic chip has unique microphysical properties and facilitates the integration of microdevices, which provides the possibility of real-time monitoring, continuous culture, separation and enrichment, and even in situ analysis of cells. In this review, we summarized recent advances in the development of different techniques for cell isolation and analysis on microfluidic platforms. Focus was put on biochemical and physical methods for cell separation on microfluidic chips. Subsequent cell analysis depending on fluorescence, Raman, cytomicroscopic imaging, mass spectrometry and electrochemical methods also was remarked. Through analyzing and learning the advantages and disadvantages of different technologies, we hope that microfluidic chips will continue to be improved and expanded for medical and clinical applications.
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