Latest ArticlesLow-cost and efficient oxygen reduction reaction (ORR) electrocatalysts are the key to developing Zn-air batteries for renewable energy storage. Herein, the Mn-N-P doped carbon sphere was prepared through polymerization of hexachlorotripolyphosphazene (HCCP) and phloroglucinol, and then followed the calcination at 900 ℃. Theory calculations demonstrated the introduction of Mn in N-P doped carbon could lower the dissociation barrier of O2 into O* and promote the ORR through a 4e− pathway. The as-prepared catalysts exhibited a half-wave potential of 0.82 V vs. RHE and limiting current density of 5.2 mA/cm2 toward ORR, which was comparable to those of the commercial Pt/C catalysts. In addition, Zn-air batteries with 0.05 Mn-N-P-C catalysts showed a high specific capacity of 830 mAh/gZn and excellent cycle stability. This facile approach demonstrated herein could be a solution to develop optimum non-precious metal catalysts for the application in cathodes of proton exchange membrane fuel cells. This study also provides new insight to design the catalysts of multi-heteroatom coordinated metal in the carbon matrix for both fundamental researches and practical applications.
Lithium-sulfur batteries (LSBs) are among the most promising series of next-generation high density energy storage systems. However, the problem of "shuttle effect" caused by dissolution and migration of polysulfide intermediates has severely inhibited their practical applications. Herein, TiO2-carbon nanocomposites embedded hierarchical porous carbon (T-hPC) interlayers are fabricated via Ti3C2 MXene assisted phase separation and annealing method. The T-hPC processes micro- to macro-scale multi-pores along with highly adsorptive and catalytic carbon supported TiO2 nanoparticles, which significantly enhances the polysulfides immobilization and improves the redox reaction kinetics when applied as lithium-sulfur battery interlayers. An initial discharge specific capacity of 1551.1 mAh/g and a stable capacity of 893.8 mAh/g after 200 cycles at 0.5 C are obtained, corresponding to a capacity decay rate of only 0.04% per cycle. The investigations in this paper can provide a simple and effective strategy to enhance the electrochemical properties for lithium-sulfur batteries.
Fe-N/C is a promising oxygen reduction reaction (ORR) catalyst to substitute the current widely used precious metal platinum. Cost-effectively fabricating the Fe-N/C material with high catalytic activity and getting in-depth insight into the responsible catalytic site are of great significance. In this work, we proposed to use biomass, tea leaves waste, as the precursor to prepare ORR catalyst. By adding 5% FeCl3 (wt%) into tea precursor, the pyrolysis product (i.e., 5%Fe-N/C) exhibited an excellent four-electron ORR activity, whose onset potential was only 10 mV lower than that of commercial Pt/C. The limiting current density of 5%Fe-N/C (5.75 mA/cm2) was even higher than Pt/C (5.44 mA/cm2). Compared with other biomass or metal organic frameworks derived catalysts, 5%Fe-N/C showed similar ORR activity. Also, both the methanol tolerance and material stability performances of as-prepared 5%Fe-N/C catalyst were superior to that of Pt/C. X-ray adsorption fine structure characterization revealed that the FeN4O2 might be the possible catalytic site. An appropriate amount of iron chloride addition not only facilitated catalytic site formation, but also enhanced material conductivity and reaction kinetics. The results of this work may be useful for the Fe based transition metal ORR catalyst design and application.
The development of effective Ru catalyst for ammonia synthesis is of important practical value and scientific significance because of the wide application of ammonia as a fertilizer and its promising applications in the renewable energy. Generally, ZrO2 was regarded as an inferior support for Ru catalyst used in ammonia synthesis. Here we prepare ZrO2 with monoclinic phase and carbon species from ZrCl4 following the preparation route of UiO-66 as well as ammonia treatment. Owing to the presence of a larger amount of hydrogen adsorption as well as the easier desorption of hydrogen species, the ill effect of hydrogen species on the nitrogen adsorption-desorption and ammonia synthesis can be effectively alleviated. The resulting ZrO2-supported Ru catalyst showed 4 times higher ammonia synthesis activity than the conventional Ru/ZrO2 obtained from zirconium nitrate.
Transition metal hydroxides/oxyhydroxides have recently emerged as highly active electrocatalysts for oxygen evolution reaction in alkaline water electrolysis, while have not yet been widely investigated for hydrogen evolution electrocatalysts owing to their unfavorable H*-adsorption, making it difficult to construct an overall-water-splitting cell for hydrogen production. In this work, we proposed a straightforward and effective approach to develop an efficient in-plane heterostructured CoOOH/Co(OH)2 catalyst via In-situ electrochemical dehydrogenation method, in which the dehydrogenated –CoOOH and Co(OH)2 at the surface synergistically boost the hydrogen evolution reaction (HER) kinetics in base as confirmed by high-resolution transmission electron microscope, synchrotron X-ray absorption spectroscopy, and electron energy loss spectroscopy. Due to the In-situ dehydrogenation of ultrathin Co(OH)2 nanosheets, the catalytic activity of the CoOOH/Co(OH)2 heterostructures is progressively improved, which exhibit outstanding hydrogen-evolving activity in base requiring a low overpotential of 132 mV to afford 10 mA/cm2 with very fast reaction kinetics after 60 h dehydrogenation. The gradually improved catalytic performance for the CoOOH/Co(OH)2 is probably due to the enhanced H*-adsorption induced by the synergistic effect of heterostructures and better conductivity of CoOOH relative to electrically insulating Co(OH)2. This work will open the opportunity for a new family of transition metal hydroxides/oxyhydroxides as active HER catalysts, and also highlight the importance of using in situ techniques to construct precious metal-free efficient catalysts for alkaline hydrogen evolution.
This study explored the catalytic mechanism and performance impacted by the materials ratio of Fe3O4-GOx composites in three typical advanced oxidation processes (AOPs) of O3, peroxodisulfate (PDS) and photo-Fenton processes for tetracycline hydrochloride (TCH) degradation. The ratio of GO in the Fe3O4-GOx composites exhibited different trends of degradation capacity in each AOPs based on different mechanisms. Fe3O4-rGO20wt% exhibited the optimum catalytic performance which enhanced the ozone decomposition efficiency from 33.48% (ozone alone) to 51.83% with the major reactive oxygen species (ROS) of O2•−. In PDS and photo-Fenton processes, Fe3O4-rGO5wt% had the highest catalytic performance in PDS and H2O2 decomposition for SO4•‒, and •OH generation, respectively. Compared with using PDS alone, PDS decomposition rate and TCH degradation rate could be increased by 5.97 and 1.73 times under Fe3O4-rGO5wt% catalysis. In the photo-Fenton system, Fe3O4-rGO5wt% with the best catalyst performance in H2O2 decomposition, and TCH degradation rate increased by 2.02 times compared with blank group. Meantime, the catalytic mechanisms in those systems of that the ROS produced by conversion between Fe2+/Fe3+ were also analyzed.
Analytical chemistry plays an important role in the qualitive and quantitative analysis for molecules in the various circumstances, especially for the high-resolution analysis. The dual-comb spectroscopy (DCS) technology with the characteristics of high resolution, high sensitivity and instantaneous sampling exhibited a great potential in high-resolution in-situ spectral methods and has been active in the fields of spatial ranging, air composition analysis, reaction monitoring and so on. In this review, we will summarize the principle of DCS according to the different wavelength coverage and overview the applications of DCS in analytical chemistry.
Solid-state materials that exhibit pressure stimulus-response characteristics in a manner of emission signal, known as piezochromic luminescence (PCL), demonstrate great potential in photoelectric devices. The weakened luminescence and insignificant color change in the aggregation state, however, hampers their practical applications. Herein, a highly emissive coordination polymer, [Zn2(H4TTPE)(H2O)4].H2O (CUST-805), is successfully constructed by employing an AIE-active chromophore as the building block. The structural characterization and photophysical properties are systematically studied. Owing to intrinsic twisted conformation and AIE feature of tetraphenylethylene-tetrazole ligand, CUST-805 achieves the visible and reversible PCL from blue to green switched by different external stimuli. The transformation between crystalline and amorphous states is proved to be the origin of present PCL behavior. Moreover, on basis of electron and energy transfer quenching mechanism, the highly selective and sensitive sensor based on CUST-805 is realized, showing the low detection limit of 0.29 ppm towards 2, 4, 6-trinitrophenol.
Fungal infections are hazardous to human health that has drawn wide attention. In this work, a specific and sensitive method combing the recognition of aptamer to (1, 3)-β-D-glucan and tyramide signal amplification technology was proposed for the in situ fluorescence imaging of fungi. Fungi could be distinctly observed by fluorescence microscope rapidly. This method provides morphology and diagnostic information for identifying fungi. The combination of aptamer and tyramide signal amplification technology is a promising tool for the detection of fungi, bacteria and even eukaryotic cell with the virtue of biomarkers.
The transformation of quantum dots (QDs) by organisms has attracted broad attention but remains unclear. Understanding of the metabolites helps to reveal the transformation pathway of QDs. Cd containing-metallothionein (MT) are the main species formed by Cd released from CdSe QDs in HepG2 cells, while speciation analysis of Cd containing MTs remains a challenge because MTs has several subisoforms and can bind with several metals. Herein, we built a hyphenated platform for speciation analysis of QDs in HepG2 cells after treatment with CdSe/ZnS QDs. The Cd-containing MTs were separated in reversed phase high performance liquid chromatography (RP-HPLC) and subsequently online detected by inductively coupled plasma mass spectrometry (ICP-MS) and electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-Q-TOF-MS) parallelly. Four groups of Cd-containing metabolites were found by detecting Cd in ICP-MS. Their structures were identified in ESI-Q-TOF-MS and further confirmed with standards of four subisoforms of MT, including N-terminal acetylation MT2a, N-terminal acetylation MT1e, N-terminal acetylation MT1g and MT1m. Each group of them contains various stoichiometry of Cd/Zn. The metabolites of QDs remain same while the concentrations of each metabolite and its stoichiometry of Cd/Zn vary for different incubation concentration/time. This work provides a new parallel hyphenation technique of HPLC-ICP-MS/ESI-MS with high separation resolution and powerful detection ability, and the obtained results provide detailed metabolism information of QDs in HepG2 cells after treatment of CdSe/ZnS QDs, contributing to deep exploration of the functional mechanisms of QDs in organisms.
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