MOF-derived Co@N-C trifunctional electrocatalysts for ORR, OER and HER have been prepared via simple and scalable method, exhibiting ultra-high catalytic activity and promising performance in Zn–air ...batteries and water-splitting.
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Development of high-efficiency non-noble electrocatalysts for oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is urgently needed for high-performance Zn–air batteries and overall water splitting. Here, a facile strategy to synthesize novel Co-MOF,O-doped carbon (Co-MOF-T) based on Zn, Co-doped glucosamine and ZIF-8 by pyrolysis at temperature T was demonstrated. The prepared Co-MOF-800 showed a superior oxygen reduction reaction (ORR) activity comparable to that of commercial Pt/C catalyst. In addition, this catalyst shows great potential in the overall water splitting due to the excellent oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities. Based on the trifunctional activity, the primary Zn–air batteries using a Co-MOF-800 air electrode achieved a high open-circuit voltage of 1.38 V, a specific capacity of 671.6 mAh gZn–1, and a prominent peak power density of 144 mW cm−2. Also, the rechargeable Zn–air batteries based on Co-MOF-800 air electrode could be smoothly run for 510 cycles with a low voltage gap of 0.58 V. Finally, the trifunctional Co-MOF-800 catalyst was applied to boost the electrochemical water splitting, demonstrating its promising potential as a green energy material for practical applications.
The electrochemical detection of hydrogen peroxide (H2O2) has become more and more important in industrial production, daily life, biological process, green energy chemistry, and other fields ...(especially for the detection of low concentration of H2O2). Metal organic frameworks (MOFs) are promising candidates to replace the established H2O2 sensors based on precious metals or enzymes. This review summarizes recent advances in MOF-based H2O2 electrochemical sensors, including conductive MOFs, MOFs with chemical modifications, MOFs-composites, and MOF derivatives. Finally, the challenges and prospects for the optimization and design of H2O2 electrochemical sensors with ultra-low detection limit and long-life are presented.
Differing from its bulk counterparts, atomically thin two-dimensional transition metal dichalcogenides that show strong interaction with light are considered as new candidates for optoelectronic ...devices. Either physical or chemical strategies can be utilized to effectively tune the intrinsic electronic structures for adopting optoelectronic applications. This review will focus on the different tuning strategies that include its physics principles,
experimental techniques, and its application of various optoelectronic devices.
This comprehensive study aimed to evaluate the water quality and sediment contamination in the Chuhe River in Nanjing. The spatial assessment of 10 samples collected in September highlighted that, in ...surface water, Copper (Cu) > Nickel (Ni) > Zinc (Zn) > Chromium (Cr) > Lead (Pb) > Arsenic (As) > Cadmium (Cd) > Mercury (Hg), whereas in sediments, Zn > Cr > Cu > Pb > Ni > As > Cd > Hg. The coefficient of variation (CV) for Ni and Zn in surface water was >15, whereas As, Cu, Pb, and Ni had a CV that was higher than 15 in sediments, indicating variability in contamination sources. The Pollution Load Index values ranged between 2.16 and 3.05, reflecting varying contamination levels across samples. The Geoaccumulation Index data also showed moderate-to-considerable contamination, especially for elements such as Cd and Cu. Correlation analyses in water and sediments unearthed significant relationships, with notable links between Cu and Pb in the water and strong correlations between As and Cu and between Cr and Ni in sediments. In sediments, Total Nitrogen and Phosphorus were significantly correlated with As, Cu, Pb, and Ni. The Potential Ecological Response Index for sediments indicated that they are at medium to high risk (307.47 ± 33.17) and could be potentially detrimental to aquatic life in the tributary. The tributary, influenced by agricultural runoff, residential areas, and other anthropogenic activities, showed that despite Nemerow pollution index values for water samples being below 1, sediment analysis indicated areas of concern. Principal Component Analysis (PCA) was conducted to identify the potential sources of heavy metal contamination. In surface water, shared negative loadings on PC 1 (60.11%) indicated a unified influence, likely from agricultural runoff, while PC 2 (14.26%) revealed additional complexities. Sediments exhibited a unique signature on PC 1 (67.05%), associated with cumulative agricultural impacts, with PC 2 (18.08%) providing insights into nuanced factors, such as sediment composition and dynamic interactions. These findings offer a complete insight into the Chuhe River tributary’s condition, underlining the urgency for ongoing monitoring and potential remediation measures.
Synopsis: A highly-efficient, economical and easily-industrialized method is developed for recycling waste LiFePO4 (LFP) battery cathode. The decay and regeneration mechanisms of LFP are deeply ...studied via microscopic characterization and electrochemical testing. Regenerated LFP achieves an excellent capacity recovery (around 99% the specific capacity of new LFP) and long-term cycling stability (over 800 cycles at 1 C). In addition, its main costs only account for 33.7% the price of new LFP.
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•An effective solid-phase method is proposed to regenerate the waste LFP.•The decay and regeneration mechanisms of LFP are studied in details.•The ionic diffusion coefficient of waste LFP is significantly enhanced by CNTs.•Regenerated LFP shows good capacity recovery and economic prospects.
Annually increasing electric vehicles will undoubtedly end in tremendous amount of waste LiFePO4 (LFP) batteries. In this work, a highly-efficient and easy-going solid-phase method is proposed for direct regeneration of the waste LFP cathode material (W-LFP). The W-LFP is successfully regenerated via heat treatment with the addition of Li2CO3, CNTs and glucose. After activation, the dispersibility of CNTs in water is improved, making it easier to mix well with other materials. Also, the hydroxyl and carboxyl groups on CNTs have a certain degree of reducibility, which is conducive to the reduction of Fe3+ to Fe2+. After subsequent heat treatment, the three-dimensional conductive network composed of CNTs greatly enhances the conductivity and the ionic diffusion coefficient of LFP, thereby improving its electrochemical performance. Meanwhile, the decay and regeneration mechanisms of LFP are investigated by characterization and electrochemical testing. The regenerated LFP achieves an excellent specific capacity of 155.47 mAh/g at 0.05 C, which is around 99% that of new LFP. Additionally, the costs of main consumption in the regeneration process only account for 33.7% the price of new LFP. This low-cost, high-value-added and solid-phase direct regeneration process is proved to have great economic and energy-saving potential, which is promising for recycling the waste LFP cathode materials.
Cobalt Prussian blue analogue Co3Co(CN)62 is used as a precursor material to obtain bamboo-shaped nitrogen-doped carbon nanotubes (Co@NCNTs-2), with low cobalt metal content through solid-state ...thermal conversion and acid pickling process. Then the active material S is combined with the host materials (Co@NCNTs-2) via a traditional melt-infusion method, the obtained cathode material shows better battery capacity and cycle stability in lithium-sulfur batteries.
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•N-doped carbon nanotubes with low Co metal content are obtained.•Co is encapsulated in the interior and N is distributed on the outside of Co@NCNTs-2.•Co@NCNTs-2 provide active sites to improve the redox reaction of sulfur cathode.•Co@NCNTs-2 shows its superiority as a cathode material host for Li-S batteries.
Functional and active carbon material is of great concern in facilitating the performance of lithium-sulfur (Li-S) battery. In this work, we develop a bamboo-like nitrogen-doped carbon nanotubes (Co@NCNTs-2) with low cobalt metal content, which acts as not only the host matrix for sulfur loading but also an efficient catalyst for the adsorption and conversion of lithium polysulfides (LiPSs). The characterization results show that the Co particles are mainly encapsulated inside the Co@NCNTs-2, and the N species are mainly distributed on the outer surface of Co@NCNTs-2. The Co particles are the growth sites of carbon nanotubes and are wrapped by carbon to form Co@NCNTs-2. It is confirmed that the uniform graphitized structure contributes to charge transfer, while the enriched N species assist the trap and catalytic conversion of the polysulfides, thus helping to restrain the shuttle effect. As a result, the resultant Co@NCNTs-2-S cathode presents high reversible capacity at different current densities and exhibits superior cycling stability for 300 cycles at 0.5 C.
The green and low-cost recycling of spent LiFePO4 (LFP) cathode materials has become an urgent problem to be solved. In this work, a completely green and easy scale-up recycling process is developed ...to recycle the cathode powders from spent LFP batteries. The optimal regeneration conditions are obtained by adjusting temperature, Li+ concentration and reductant dosage. Meanwhile, the mechanism of regeneration is investigated by microscopic characterization and electrochemical performance testing. The regenerated LFP shows a good discharge specific capacity of 148 mAh/g at 0.05 C, which exhibits around 96% the capacity of raw LFP. Additionally, the costs of the consumption only account for 19.8% the price of raw LFP, which indicates that this method has good prospect of economic returns. This regeneration method is low in cost, simple in process, mild in conditions and easy to scale up, providing technical supports for the sustainable development of lithium-ion battery industry.
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•A green and low-cost method has been proposed to regenerate the spent LiFePO4.•The decay and regeneration mechanisms of LFP are discussed in details.•The regenerated LFP shows a good discharge specific capacity recovery.•The costs of the consumption only account for 19.8% the price of raw LFP.
An effective composite of natural microcrystalline graphite/low density polyethylene (MG/LDPE) was prepared by extrusion calendering method and the electromagnetic absorption properties of the ...composites were investigated. The morphology and structure of the MG were characterized by scanning electron microscopy, energy-dispersive X-ray microanalysis system, Raman spectroscopy and X-ray diffraction. It is interesting to find that two absorbing peaks appear at low frequency and high frequency with the thickness of 2.0–2.1mm. Results show that the content and the particle size of MG have great effects on the electromagnetic absorption property of the MG/LDPE composites. Under the condition that the speed of ball-milling is 800r/min, the bandwidth of MG/LDPE composites less than −5dB reaches 6.79GHz, its less than −10dB comes to 3.02GHz, and the reflectivity values are −12.44dB and −20.46dB. The remarkable electromagnetic absorption properties of MG/LDPE composite can attribute to the multiple absorbing mechanisms. It is believed that such a composite could serve as an attractive candidate for electromagnetic absorbers.
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•An effective composite of natural microcrystalline graphite/low density polyethylene was prepared by extrusion calendering method.•It is interesting to find that two absorbing peaks appear at low frequency and high frequency with the thickness of 2.0–2.1mm.•The remarkable electromagnetic absorption properties of composite can be attributed to the multiple absorbing mechanisms.•It is believed that such a composite could serve as an attractive candidate for electromagnetic absorbers.
Despite the difficulty in the orientational growth control for two-dimensional (2D) materials due to the large anisotropy of surface energy, here we propose a simple growth strategy by adjusting the ...spatial distribution of the gas flow to tune the vertical/planar growth of nonlayered Cr-based chalcogenide nanoplates. The vertical growth nucleation behaviors are directly related to the distribution of the gas flow and precursor concentration, which are formed by stacking silicon substrates to change the transportation behaviors of the precursor species. The elemental growth steps including nucleation, oriented growth, and the interface formation between the as-grown samples and substrates are characterized by electron microscopy, which concluded that the nucleation of the vertical nanoplates is either achieved from random pregrown polycrystalline nanocrystals or from the amorphous buffer layers. The thickness and density of the nanoplates can be controlled by tuning the height of the airflow barrier and growth conditions. Moreover, an electrostatic-assistance method has been developed to transfer the vertically grown nanoplates to arbitrary surfaces, which could retain very weak interaction with the substrate that largely reduces the electronic influence from the substrates. Our results not only provide a new universal vertical/planar growth method for 2D materials but also hint at a new possibility of pursuing intrinsic 2D magnetic properties and opening the door to explore various 2D magnetic applications and high surface-area-derived applications.
Two-dimensional (2D) magnets have raised enormous attention because of their stable long-range magnetic orders and anomalous magnetic physics at 2D limits. Spin glass states are normally discovered ...in disordered systems with spin frustration, which are rarely found in 2D crystalline materials. Here, the chemical vapor-deposited rhombohedral Cr2Se3 nanosheets could be grown down to a thickness of 1.9 nm, which have shown a hard magnetism of large coercivity of 1.5 kOe and exhibited thermal irreversibility. A spin glass state with a freezing temperature of 28 K can be estimated from an alternating-current magnetic susceptibility survey, in which unambiguous magnetic response evidence of a spin glass state in crystalline Cr2Se3 nanosheets was shown. An extracted short relaxation time of 10–13 s and atomic magnetic frustration that were confirmed by neutron diffraction could strongly suggest the spin glass state with an atomically short-range magnetic order in the Cr2Se3 nanosheets.
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