Hollow MnFe2O4 nanocubes assembled by CoS2 nanosheets are fabricated by an effective strategy for hybrid supercapacitors.
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•Hollow MnFe2O4 nanocubes were prepared by calcination of ...MnFe-PBA.•CoS2 nanosheets were formed on MnFe2O4 nanocubes by hydrothermal method.•CoS2 acts as the structure protector to prevent the collapse of MnFe2O4.•The as-prepared nanomaterial shows good electrochemical properties.•A hybrid supercapacitor delivers high energy density.
Even though the transition metal oxides (TMOs) are theoretically favorable for supercapacitors, the low electrical conductivity and durability hinder their major practical application. Designing TMOs with innovative nanostructures and unique properties is an effective strategy to overcome these limitations and boost their electrochemical properties. Considering this, in this research, we design hollow MnFe2O4 nanocubes assembled by CoS2 nanosheets (designated as HMFO-CSN) and evaluate its supercapacitive performance where it is used as a cathode electrode in the hybrid supercapacitors. The nanostructuring strategy used here includes three steps (i) MnFe-Prussian blue analogue (MnFe-PBA) nanocube formation, (ii) calcination of the MnFe-PBA to produce MnFe2O4 hollow structures, and (iii) growing CoS2 nanosheets on the product through the hydrothermal process to get the final product, i.e., HMFO-CSN. The hollow MnFe2O4 nanocube which acts as the effective skeleton can fasten electron transportation and ion diffusion. Meanwhile, the existing porous CoS2 nanosheet is not only served as an effective outer layer to enhance conductivity but also acts as a structure protector to prevent the collapse and degradation of inner MnFe2O4 hollow nanocube during stability test. Benefiting from such merits, the as-synthesized nanomaterial shows a capacity of 894C g−1 at 1 A g−1 with a rate capability of 76.2% (681.25C g−1 at 48 A g−1), and excellent 90.5% capacity retention at 12 A g−1 after 10,000 cycles. Furthermore, the hybrid supercapacitor made of HMFO-CSN (cathode electrode) and activated carbon (AC, anode electrode) delivers an energy density of 63.75 Wh kg−1 at 850 W kg−1 with high longevity of 88.5% after 10,000 cycles at 12 A g−1. The developed synthetic method may offer new inspirations for the fabrication of high-performance electrode materials with advanced structures for various energy-related applications.
•Low-cost material modified laser scribed graphene (LSG) aptasensor is developed.•ZnFe2O4 modified LSG increased the sensitivity of cardiac troponin-I (cTn-I) aptasensor.•LSG-ZnFe2O4-aptasensor ...exhibited a low limit of detection up to 0.001 ng/mL.•The aptasensor is practically feasible to detect cTn-I in human serum samples.
Laser-scribed graphene (LSG) electrodes have gained significant interest due to the ease in fabrication, surface modification, and potential to develop various types of electrochemical sensors and biosensors. In these studies, a new type of zinc ferrite nanoparticles (ZnFe2O4 NPs) modified LSG electrochemical sensing system comprising LSG-ZnFe2O4 working electrode, LSG reference, and LSG counter electrode on a single polyimide substrate is presented. LSG-ZnFe2O4 electrodes are fabricated by drop-casting a solution of ZnFe2O4 NPs onto the LSG electrode, which gave a 31% enhancement of sensitivity and electrocatalytic activity compared to the bare LSG electrode. LSG-ZnFe2O4 electrochemical aptasensor for acute myocardial infarction (AMI) screening is developed by detecting the cardiac Troponin-I (cTn-I) biomarker. The results show that the developed aptasensor could detect a broad concentration range of cTn-I with a limit of detection of 0.001 ng/mL and a sensitivity of 19.32 (±0.25) µA/(ng/mL). In addition to this, LSG-ZnFe2O4-aptasensor shows higher selectivity towards the detection of cTn-I and negligible cross-reactivity with other interfering biomolecules. Finally, it is demonstrated that LSG-ZnFe2O4-aptasensor can easily detect different concentrations of cTn-I spiked in human serum samples. These results show that the LSG-ZnFe2O4-aptasensor is a promising diagnostic tool to monitor cTn-I and could be a potential candidate to develop point-of-care devices for cTn-I biomarker detection and various other disease biomarkers in the future.
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In recent years, many researchers have begun to shift their focus onto the synthesis of nanomaterials as this field possesses an immense potential that may provide incredible technological advances ...in the near future. The downside of conventional synthesis techniques, such as co-precipitation, sol-gel and hydrothermal methods, is that they necessitate toxic chemicals, produce harmful by-products and require a considerable amount of energy; therefore, more sustainable fabrication routes are sought-after. Biological molecules have been previously utilized as precursors for nanoparticle synthesis, thus eliminating the negative factors involved in traditional methods. In addition, transition-metal nanoparticles possess a broad scope of applications due to their multiple oxidation states and large surface areas, thereby allowing for a higher reactivity when compared to their bulk counterpart and rendering them an interesting research topic. However, this field is still relatively unknown and unpredictable as the biosynthesis of these nanostructures from fungi, bacteria and plants yield undesired diameters and morphologies, rendering them redundant compared to their chemically synthesized counterparts. Therefore, this review aims to obtain a better understanding on the plant-mediated synthesis process of the major transition-metal and transition-metal oxide nanoparticles, and how process parameters—concentration, temperature, contact time, pH level, and calcination temperature affect their unique properties such as particle size, morphologies, and crystallinity.
In this work, g-C3N4@NiMoO4/CoMoO4 (gCN@NCM) was fabricated by a hydrothermal method. g-C3N4 sheets were embedded in staggered NiMoO4/CoMoO4 rods to form a three-dimensional structure. The prepared ...gCN@NCM exhibited good electrochemical performance of high specific capacitance (641.5 F/g) and excellent cycle stability (15.79% of capacitance lost after 8000 cycles). The specific capacitance of the gCN@NCM//active carbon (AC) device got 30% enhanced at the first 2000 cycles. Moreover, 110% of the original specific capacitance was still maintained after 10,000 cycles. These results indicate that the g-C3N4@NiMoO4/CoMoO4 has great potential in supercapacitors.
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•Combining g-C3N4 with ternary transition metal oxides helps to enhance the electrochemical performance.•The special three-dimensional structure provides large surface area for the redox reaction.•g-C3N4 accumulating on the NiMoO4/CoMoO4 rods limits the electrochemical properties.•g-C3N4 based flexible supercapacitor exhibited excellent 110% of the original specific capacitance after 10,000 cycles.
High entropy oxide (HEO) is a new-type inorganic material composed of multiple principle metal elements with a single-phase structure and is proved to display many potential unexpected properties ...such as high structural stability and superionic conductivity. Herein, a novel spinel-structured high entropy oxide (FeCoNiCrMn)3O4 is prepared by high-temperature solid state reaction and evaluated as anode for lithium-ion batteries (LIBs). In-situ high-temperature X-ray diffraction (HT-XRD) is used to reveal structure evolution of mixed oxides with the calcination temperature increase and a single-phase spinel-structured (FeCoNiCrMn)3O4 is obtained at 900 °C. The effect of temperature on structure and electrochemical performance of HEO were investigated, and the HEO-900 anode with commercial mass loading exerts higher capacity (discharge/charge, 1034/680 mAh g−1) and better rate capability (182 mAh g−1 at 2 Ag-1) than HEO-950 and HEO-1000 for its moderate particle size, and all the three samples show excellent cycling stability. Ex-situ XRD and transmission electron microscope are applied to unravel the lithium-storage mechanism of (FeCoNiCrMn)3O4, an amorphization reaction process occurs during the initial discharging and the amorphous structure is maintained in subsequent cycles. The synergetic effect of multiple metal cations with different radius, valence states and reaction potentials and entropy stabilization effect make the HEO display a superior electrochemical performance in LIBs. This work provides a new concept to design multi-element transition metal oxide anode materials by high entropy strategy.
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•A spinel-typed high entropy oxide (FeCoNiCrMn)3O4 is prepared by solid state reaction.•In-situ high temperature XRD is used to reveal structure evolution of HEO formation.•The high entropy oxide is explored as an anode material for lithium-ion batteries.•Well-mixed cations make HEO show a excellent cycling stability and rate capability.
Energy density of lithium ion batteries based on transition metal oxide cathodes can be enhanced by increasing the end-off charge voltage to a great extent, because the cathodes can deliver a larger ...specific discharge capacity under an elevated charge voltage. However, this operation is always accompanied by the oxygen evolution from the cathode oxides, which might cause the crystal destruction of the cathode oxides and the severe electrolyte decomposition on the cathodes, leading to the fast failure of the batteries. In this work, we report a new finding that the oxygen evolution in graphite/LiNi0.6Mn0.2Co0.2O2 pouch cell can be efficiently suppressed and thus the cyclic stability of the cell is significantly improved by using tributyl borate (TBB) as electrolyte additive, even under 4.5 V. Electrochemical tests indicate that, with adding 1 wt% TBB to the electrolyte, the capacity retention of the cell is enhanced from in 35.1% to 94.9% after 120 cycles. The physical characterizations combining theoretical calculations demonstrate that the B-containing species in the cathode electrolyte interphase, originated from the oxidation of TBB, present a strong combination with oxygen and suppress efficiently the oxygen evolution.
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Lead salts poisoning was a great challenge for the catalysts application in selective catalytic reduction (SCR) reaction of NOx with NH3 in stationary sources. Herein, several typical transition ...metal (Cu, Co and Zr) oxides modified Mn-Ce/AC catalysts were prepared by impregnation method, and the effects of Cu, Co and Zr doping on resistance PbCl2 poisoning for the catalyst were investigated. The addition of three transition metal oxides improved the PbCl2 resistance of Mn-Ce/AC catalyst and maintained excellent low-temperature denitrification activity of the catalyst. The lead resistance performance of the three metal oxides followed: Cu > Co > Zr oxides. The NO conversion of Cu-doping catalyst after PbCl2 poisoning was only ca. 10% lower than that of fresh Mn-Ce/AC catalyst at 225 °C. Cu, Co and Zr doping could decrease the loss of specific surface area caused by poisoning, while Cu-doped catalyst showed lowest crystallinity of active components. Meanwhile, the contents of Mn4+ and chemisorbed oxygen in Cu-doped catalyst were higher than those in Co- or Zr-doped catalysts. Cu, Co and Zr doping improved the surface acidity and redox performance of the poisoned catalysts, with Cu-doped poisoned catalyst exhibiting nearly the same surface acidity and redox performance as the fresh Mn-Ce/AC catalyst. Furthermore, Cu doping could also improve NO adsorption and was in favor to the SCR process. Besides, in situ DRIFTS results showed that the catalytic reaction pathways of all the poisoned or modified catalysts were in accordance with both Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms. Finally, a possible anti-PbCl2 poisoning mechanistic model of (Cu, Co and Zr) oxides modified on Mn-Ce/AC catalyst was proposed.
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•Cu-modified MC/AC catalyst showed best resistance to PbCl2 poisoning.•Transition metal oxides alleviated damage of PbCl2 to MC/AC structure.•Redox ability and acidity of PbCl2-poisoned catalyst were promoted by modifying.•NH3-SCR reaction on PbCl2-poisoned catalyst followed L-H and E-R mechanism.
The Earth‐abundant and inexpensive manganese oxides (MnOx) have emerged as an intriguing type of catalysts for the water oxidation reaction. However, the overall turnover frequencies of MnOx ...catalysts are still much lower than that of nanostructured IrO2 and RuO2 catalysts. Herein, we demonstrate that doping MnOx polymorphs with gold nanoparticles (AuNPs) can result in a strong enhancement of catalytic activity for the water oxidation reaction. It is observed that, for the first time, the catalytic activity of MnOx/AuNPs catalysts correlates strongly with the initial valence of the Mn centers. By promoting the formation of Mn3+ species, a small amount of AuNPs (<5 %) in α‐MnO2/AuNP catalysts significantly improved the catalytic activity up to 8.2 times in the photochemical and 6 times in the electrochemical system, compared with the activity of pure α‐MnO2.
Just a pinch: A small amount of dopant gold nanoparticles (<5 %) increased the catalytic activity of α‐MnO2 in water oxidation reactions with the established Ru(bpy)32+–S2O82− system (bpy=2,2′‐bipyridine) by up to 8.2‐fold in the photochemical and sixfold in the electrochemical system. The nanoparticle dopant is thought to mediate the electron‐transfer steps in the mechanism as shown.
In the present study, we prepared vacancy-engineered V2O5-x films for electrochromic (EC) applications. To investigate the vacancy effect of V2O5-x films with high EC performance capabilities, ...precursor concentrations of V-based sol solutions were varied at 1 wt%, 5 wt%, and 10 wt%. Among them, V2O5-x films with a precursor concentration of 5 wt% (V2O5-5wt%) showed superior EC performance outcomes due to the (001)-plane-oriented crystal structure, which provides high electrical conductivity with the oxygen vacancy (Vo). In addition, the gravel-like uniform surface morphology with the optimized film thickness provides a stable electrochemical reaction during the EC measurement. As a result, V2O5-5wt% exhibited fast switching speeds (2.1 s for coloration and 3.6 s for bleaching), high transmittance modulation (ΔT) (51.32%), high coloration efficiency (CE) (52.3 cm2/C), and excellent cycle stability (85.85% ΔT retention after 500 cycles). In addition, V2O5-5wt% showed energy storage capability of 443.7 F/g at a current density of 2 A/g, thus proving its potential for use in multi-functional applications. Therefore, these results provide valuable insight related to the engineering of vacancies in EC films to achieve high-performance EC devices and additional multi-functional applications.
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