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(a) XRD patterns of the as-prepared NiCo 2 O 4 /MnCo 2 O 4 and (b and c) structure illustration of spinel NiCo 2 O 4 and MnCo 2 O 4 .
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The rational design of three-dimensional (3 D) hierarchical porous architectures possessing the advantages of improved electrical conductivity and reduced volume change during the charge/discharge processes has been proved to be an effective way for enhancing the electrochemical performance of binary metal oxides and related hybrids. Herein, unifor...
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... 3D porous rose-like NiCo 2 O 4 /MnCo 2 O 4 and NiCo 2 O 4 can be obtained by calcining Ni-Co-Mn-based precursors and Ni-Co-based precursors at 350 C for 2 h (the related SEM, TEM and EDX mapping images are shown in Fig. S1 †), respectively. Thermogravimetric analysis (TGA) is conducted to investigate the thermal decomposition behavior of the Ni-Co-Mn-based precursor. Fig. S2 † shows that the Ni-Co-Mn-based precursors exhibit a sharp weight loss between 200 and 250 C. Therefore, the Ni-Co-Mn-based precursors were calcined at 350 C for 2 h to obtain the nal ...
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... behavior of the Ni-Co-Mn-based precursor. Fig. S2 † shows that the Ni-Co-Mn-based precursors exhibit a sharp weight loss between 200 and 250 C. Therefore, the Ni-Co-Mn-based precursors were calcined at 350 C for 2 h to obtain the nal products. The representative X-ray diffraction (XRD) patterns of the as-prepared nal products are shown in Fig. 1a. All of the diffraction peaks can be indexed and assigned to NiCo 2 O 4 [JCPDS card no. 73-1702, a ¼ 8.114Å114˚114Å, space group Fd3m (227)] or/and MnCo 2 O 4 [JCPDS card no. 23-1237, a ¼ 8.269Å269˚269Å, space group Fd3m (227)]. 6,15 There are no impurity peaks such as Mn x O y observed in the product. The diffraction peaks of the ...
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... C for 2 h) ( Fig. S3 †) can be indexed to NiCo 2 O 4 (JCPDS card no. 73-1702), and no impurities are found in this XRD pattern. The parameters of the composite and individual two binary metal oxide XRD peak positions are displayed in Table S1, † revealing the slight displacement shiing phenom- enon. The crystallographic structure of NiCo 2 O 4 ( Fig. 1b) shows that the nickel ions occupy the octahedral sites, while in the MnCo 2 O 4 ( Fig. 1c), the manganese ions are distributed in tetrahedral and octahedral sites. 15,16 The Raman spectra ( Fig. S4 and Table S2 ...
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... are found in this XRD pattern. The parameters of the composite and individual two binary metal oxide XRD peak positions are displayed in Table S1, † revealing the slight displacement shiing phenom- enon. The crystallographic structure of NiCo 2 O 4 ( Fig. 1b) shows that the nickel ions occupy the octahedral sites, while in the MnCo 2 O 4 ( Fig. 1c), the manganese ions are distributed in tetrahedral and octahedral sites. 15,16 The Raman spectra ( Fig. S4 and Table S2 ...
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... the experimental parameters (such as the temperature or the treatment process for the product) and the structure of the composite may play important roles in arousing the frequency shis and band broadening of the Raman behavior, 22 however, the exact reason still needs further research. This result is consistent with that of the XRD patterns (Fig. 1a). Elemental composition analysis of the mixed oxides obtained with an energy dispersive spectrometer (EDS) further certicates the existence of nickel, cobalt, manganese and oxygen elements (Fig. S5 ...
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... subsequent cycles, the main reduction peak shis to 0.86 V and there is an obvious intensity decline of both anodic and cathodic peaks aer the rst cycle. From the second cycle onwards, the CV curves overlap very well, indicating the good reversibility of the electrochemical reac- tions. Compared with the CV curves of the NiCo 2 O 4 electrode (Fig. S10 †), the oxidation peak centered at 2.24 shis to 2.01 V, which reects the intimate interaction between NiCo 2 O 4 nanosheets and MnCo 2 O 4 nanoparticles. This could reduce the electrode polarization and improve the charge-transfer kinetics, leading to a much higher capacity. 30 Based on the above analysis and previous reports, 6,15 the ...
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... which "i" is the current density, "v" is the potential sweep rate, and "a" and "b" are adjustable parameters. Accordingly, for battery behavior, the b-value approaches 0.5 and the Li + inser- tion process dominates. In contrast to battery behavior, when the b-value is close to 1, the system is mainly controlled by capacitance. Fig. S11b † shows the log i vs. log v plots at different oxidation or reduction states, indicating that the b-value approaches 1. Therefore, the NiCo 2 O 4 /MnCo 2 O 4 is mainly controlled by the capacitive process aer 350 cycles, which leads to fast Li + insertion/extraction (high rate property) and extended cycling life. 5,[33][34][35][36] ...
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... controlled by the capacitive process aer 350 cycles, which leads to fast Li + insertion/extraction (high rate property) and extended cycling life. 5,[33][34][35][36] The inuences of different ratios of the active materials, acetylene black and CMC (such as 50 : 30 : 20 and 70 : 20 : 10) on the capacities of the product were evaluated (see Fig. S12 This journal is © The Royal Society of Chemistry 2015 preserves the morphology and surface feature, suggesting its relative high morphology ...
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... each cubic structure is densely interconnected with perpendicular direction at corners in 3D structure, offering rough surface with high surface area, which is beneficial for hydroxyl ion (OH À ) accessibility at the electrode-electrolyte interfacial surface during the electrocatalysis process. [36] Confirmed with CV technique, the electrochemical surface area (ECSA) of catalyst samples is examined in O 2 and N 2 saturated KOH, revealing that all catalysts possess high ECSA values (Table S5) Table S2, which is well consistent with Ni-doping contents. ...
Herein, an effective strategy using defect engineering promoted by Ni atom doping on MnCo2O4 is proposed for bifunctional catalytic activities of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). A series of NixMn1‐xCo2O4 with x=0, 0.1, 0.2, and 0.3 is hydrothermally synthesized. Tuning the electronic structure by Ni‐doped MnCo2O4 results in modulating the valence states by dominating Mn⁴⁺ / Co³⁺ with the increase of oxygen vacancies. At optimized Ni content, Ni0.2Mn0.8Co2O4 reveals activity toward ORR with a current density of −1.02 mA cm‐2 at 0.95 V (vs. RHE), a high electron transfer number of 3.536, and the highest half‐wave potential of 0.855 V, which is comparable to Pt/C. For OER, Ni0.2Mn0.8Co2O4 demonstrates the lowest overpotential of 503 mV to achieve a current density of 10 mA cm⁻². Additionally, rechargeable zinc‐air batteries (RZABs) with Ni0.2Mn0.8Co2O4 catalyst demonstrate a capacity of 808.6 mA h g⁻¹ at 1.0 mA cm⁻² with power densities of 459 mW cm⁻² at 675 mA cm⁻². The improved binding strength (Mn−O/Co−O bond) and the enhanced stability by Ni atom doping in MnCo2O4 for ORR/OER is proved by ex‐situ FT‐EXAFS. This work highlights defect engineering on Ni‐doped MnCo2O4 used as bifunctional ORR/OER catalysts for high‐performance RZABs.
... [21][22][23]. Recently, various morphologically distinct NiCo 2 O 4 based nanostructures have been synthesized, like nanoparticles [24], nanoflakes [25], nanoneedles [26], nanowires [27], nanoribbons [28], and nanoflowers [29], etc. These nanomaterials manifest extraordinary electrochemical properties because of their enormous voids, expanded surface area, and reduced pathways for efficient electrolyte ion transport [30,31]. ...
... The structural and phase features of MCO, MCO/TCX, and MCO/ MWCNT are displayed in Fig. 2(a) characterized by the X-ray diffraction technique. The reflection of the peaks observed in Fig. 2(a) [34,35]. It is evident that MCO decorated over MXene sheet, revealing a consistent layered- ...
The logical construction of electrode materials along with greater electrochemical features and solid architectural design is a strategic approach for boosting the electrochemical performance of supercapacitors. However, it is tough and complicated to develop diverse composite materials with better electronic conductivity and greater specific capacitance via rapid and cost-effective synthesis procedures. Herein, we propose a straightforward and simple approach by employing the hydrothermal technique for the synthesis of spinel MnCo2O4 composite nanostructures using 1D MWCNT and 2D MXene (Ti3C2Tx) materials with detailed analysis of the supercapacitor performance as compared to existing literature on similar studies. The MCO/TCX (MnCo2O4/Ti3C2Tx) composite shows an impressive capacitance of 860.22 F/g at a current density of 2 A/g after electrochemical optimization. Furthermore, an asymmetric supercapacitor device (ASCs) was constructed using MCO and its composites MCO/MWCNT and MCO/TCX as a positive, and AC was employed as a negative electrode to test its device capability. Comparatively, the MCO/TCX//AC SC device demonstrated exceptional energy storage properties with a better specific capacitance value of 126.58 F/g at 0.8 A/g of current density, an elevated energy density of 40 Wh/kg, with a power density of 4828 W/kg along a capacitance retention rate of 87 % over 5000 cycles, suggesting better cycle life. Whereas, the MCO/MWCNT//AC device shows a better cycling performance of 91 % after 5000 cycles with a superior energy and power density of 27.04 Wh/kg and 1448 W/kg respectively. Also the theoretical insight for further understanding of the charge-storage mechanism through DFT calculations provides an estimate of electronic properties and quantum capacitance calculated for the pristine MCO and its hybrids with CNT and Ti3C2Tx MXene and information on the interactions between orbitals, the bonding process, and the charge transfer capabilities of each electrode material. The theoretical studies also confirm that the electronic properties and therein charge storage performance have an increasing trend in the order of MCO < MCO/CNT < MCO/TCX consistent with the experimental findings. Additionally, these simulations conclude that the hybrid MCO/TCX has the largest quantum capacitance which is in accordance with the findings of the experiments. The improved performance of MCO/TCX is due to the enlarged surface area that allows higher charge transfer from TCX to MCO. The charge transferred from the C 2p orbital of TCX to the Mn 3d orbital of MCO is the leading cause for the capacitance improvement mechanism of hybrid MCO/TCX. This work offers a simple procedure for developing energy storage devices using spinel MnCo2O4-based compositeelectrode materials supported by 1D carbon nanotube and 2D MXene that offer superior electrochemical performance and the fabricated electrodes that could be employed further for energy storage-based applications
... PDF-00-058-1638) [26,27], and other multiple peaks ascribed to the NCO catalyst (card no. PDF-00-020-0781) [28,29] (see Fig. 2(a)). On the other hand, m-BAE shows a major contribution of Ni conductive additive (card no. ...
Secondary zinc-air batteries (ZABs) offer a promising alternative for the future of sustainable energy storage. However, the current capability of secondary ZABs is far from satisfactory. The limitations for achieving high reversibility are mainly related to the bifunctional air electrodes as it severely hampers practical applications and commercialization of secondary ZABs. Many efforts have been devoted to the development of efficient and corrosion resistant bifunctional electrocatalysts towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In ZABs, carbon is commonly used as conductive additive, however, it has been observed that carbon materials are not resistant to the high positive voltages applied in electrical recharge. In this work, the use of metallic nickel as alternative conductive additive in bifunctional air electrodes is explored and compared with carbon nanotubes (CNT). We demonstrate that the chemical resistance of CNT does not limit the electrode performance; but the density of the additive as well as its interaction with the active material is crucial for achieving long cycle life. The use of Ni as conductive agent in secondary ZABs boosted the cycle life by delivering more than 2,400 cycles, in contrast to the 88 cycles delivered by the analogous carbon-based battery.
... The XRD characterization can determine the phase composition and crystallinity of MnCo 2 O 4 and MnCo 2 O 4 @NC composites are shown in Fig. 2 [27]. After comparing to bare MnCo 2 O 4 , all the MnCo 2 O 4 @NC composite materials show a slight negligible peak shift, indicating that the cubic crystalline phase of MnCo 2 O 4 is unaffected by NC. ...
... MnCo 2 O 4 porous sphere morphology is well preserved on MnCo 2 O 4 @NC-2 composite and shell thickness of nitrogen-doped carbon around 70e80 nm. The HR-TEM image of MnCo 2 O 4 @NC composite shows lattice d-spacing of 0.9 nm, which corresponds to the (311) for planar distance [27], is shown in Fig. 4e. The selected area electron diffraction (SAED) pattern shown in Fig. 4f exhibits crystalline nature of MnCo 2 O 4 porous composite. ...
Spinel-based nanostructured materials are commonly used as promising electrode materials for supercapacitor applications. The combination of heteroatom-doped carbon material with spinel oxides substantially improves the specific capacitance and cyclic stability. In this work, dopamine-derived nitrogen-doped carbon was coated on spinel phase MnCo2O4 nanospheres using simple solvothermal and calcination methods. Surface morphology and the crystalline structure of the prepared MnCo2O4@Nitrogen-doped carbon were confirmed by FESEM and X-ray diffraction. The electrochemical performance of MnCo2O4@Nitrogen-doped carbon electrode material was analyzed by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy techniques. MnCo2O4@nitrogen-doped carbon exhibits the highest specific capacitance of 1200 F/g compared to MnCo2O4 spheres are 726 F/g at 1 A/g and exhibits excellent cyclic stability (capacitance retention of 87% at 7 A/g after 3000 cycles). The enhanced performance of the composite might be benefitted from the synergistic effect between nitrogen-doped carbon on porous MnCo2O4 spheres. Furthermore, an asymmetric supercapacitor device was fabricated by using the optimized composition of MnCo2O4@NC-2 as a positive electrode and nitrogen, sulfur-doped reduced graphene oxide (NS-rGO) as a negative electrode, respectively. This asymmetric supercapacitor device achieves a maximum energy density of 61.0 Wh/kg at a power density of 2889 W/kg and possesses excellent capacitance retention of 95% after 5000 cycles at 7 A/g.
... 73-1702). No other peaks corresponding to NiO or CoO was found which indicates the formation of pure phase NiCo 2 O 4 [24]. ...
Due to increasingly stringent rules, eliminating pollutants (NOx) emitted by diesel engines in the automobile sector remains an intriguing scientific and technological problem. To meet the strict NOx emission restrictions, a catalytic system with a high level of complexity, unit size, and quantity, as well as higher fuel consumption, is required. As a result, for a reduction in individual exhaust gas emissions, an after-treatment system for a diesel vehicle must employ integrated catalyst technology. For selective catalytic reduction of NOx without any external reductant, a highly effective catalyst “spinel nickel cobaltite” (NiCo2O4) was produced using a polymeric precursor technique. In this work, an exhaust gas treatment system without external reductants using nano-NiCo2O4 as catalyst was designed and fabricated, for NOx control in diesel and petrol engines at low temperature. In order to determine the NOx conversion efficiency in the selective catalytic reduction system, tests were carried out at different engine loads. The system was supposed to be cost-effective due to the nano-NiCo2O4 catalyst’s ability to work at low temperatures. The findings proved the developed SCR system’s potential to reduce NOx emissions. At a high load, the nitric oxide (NO) emissions were reduced by 54 and 96 percent, respectively, without increasing HC, CO, and CO2 emissions or compromising efficiency.
... 47,48 In the case of the MnCo 2 O 4 /CNTs sample, the diffraction peaks that corresponds to the standard spectrogram of MnCo 2 O 4 (JCPDS card file Number: 23-1237) was obtained. [49][50][51] The characteristic peaks appeared at two theta around 18.5°, 30.5°, 36°, 44°, 54°, 60°and 64°are corresponding to the crystal planes (111), (220), (311), (400), (422), (511), (440) respectively. On the other hand, GO nano-sheets showed a diffraction peak (002) at 2θ = 10.8°with ...
... Thus, the crystal structure of MnCo 2 O 4 /GO was confirmed by the XRD diffraction analysis, which is consistent with the standard spectrogram of MnCo 2 O 4 (JCPDS card file Number: 23-1237). [49][50][51] A weak broad peak was appeared at 26°referring to the TRGO characteristic peak because the sample was calcinated at 300°C which led to thermal reduction of GO as mentioned in the above section. The reflection planes of [52][53][54] On the other hand, the crystallite size Dv of the nanomaterials was calculated using. ...
Bimetallic oxide/carbon nanomaterials hybrids were chemically synthesized and fully characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The elemental data analysis confirmed the successful formation of MnCo2O4/carbon nanomaterials. The fingerprint area of FTIR showed the incorporation of the metal oxides onto CNTs and GO surfaces. Morphological investigations of the nanocomposites, using FESEM and HRTEM, revealed the uniform distribution of bimetallic oxide nanostructures over the surface of carbon nanomaterials. Furthermore, electrochemical characteristics were explored using the CV and EIS. The obtained electrochemical results demonstrated significant improvements in the electrocatalytic properties, in addition to the direct and fast electron transfer provided by the modified surfaces whereas MnCo2O4/CNTs were exploited for the nano-enzymatic detection of hydrogen peroxide as an example to show the promising applications of such materials in designing non-enzymatic sensors and biosensors.
... All diffraction peaks in the XRD patterns of NiO, Co 2 O 3 , and NiCo 2 O 4 MOF-derived materials can be readily indexed to JCPDS card No. of 00-022-1189, 01-074-2120, and 01-073-1702, respectively, and no characteristic peaks referred to possible impurities. According to the XRD pattern, NiCo 2 O 4 MOF-derived adopts cubic spinel-related structures with a space group of Fd3m , in which Ni ions are embedded in the octahedral region, and Co ions occupied both octahedral and tetrahedral region [18][19][20] . ...
Herein, a novel core in hollow shell NiCo2O4 (CHS-NCO) metal-organic framework is designed using aurin tricarboxylic acid as a three-organic dental ligand for supercapacitor and hydrogen evolution application. The XRD results and FE-SEM images confirm the formation of NiCo2O4 and the spherical structure of NiCo2O4. TEM images demonstrated the core in the hollow shell structure of NiCo2O4 metal-organic framework derived. The as-prepared material shows the highest specific capacitance of 531 and 695 F g–1 in KOH and K3Fe(CN)6 (10.0 mmol L–1), respectively. Furthermore, the NiCo2O4/activated carbon battery-like supercapacitor device with a high operating potential window of 1.60 V is assembled and shown excellent energy density, power density, and durability electrolytes. The as-prepared battery-like supercapacitor device can light up three color LEDs for more than 60 minutes. This noticeable performance suggests the potential use of CHS-NCO material as a positive electrode for high-performance battery-like supercapacitors and electronic devices. Also, the HER electrocatalyst shows the Tafel slope of 69 and 81 mV dec–1 for Pt and graphite counter electrode, respectively. The current density of 10 mA cm–2 achieves at the potential of -0.17 and -0.38 V (vs. RHE) for Pt and graphite counter electrode, respectively, and the electrode material exhibits high long-cycle life acidic media. So it is a good candidate for HER.
... Peaks at 862.41 eV and 881.08 eV correspond to the satellite peaks of Ni 2+ 2p 3/2 and Ni 2+ 2p 1/2 , respectively, in h-MCO/NiPi, and peaks at 861.74 eV and 880.36 eV correspond to the satellite peaks of Ni 2+ 2p 3/2 and Ni 2+ 2p 1/2 , respectively, in NiPi. 26 Fig. S3(b) (ESI †) shows the core level XPS spectra of P 2p for h-MCO/NiPi and NiPi; they de-convolute to give 2p 3/2 and 2p 1/2 peaks at 133.25 eV and 134.10 eV in the composite, and at the binding energies of 133.12 eV and 134.07 eV in the bare NiPi electrode. This confirms the presence of phosphorus in the phosphate form in both the electrodes. ...
... eV are assigned to the satellite peaks of the Co 2p h-MCO/NiPi electrode. Similarly, peaks at 780.19 eV and 795.42 eV correspond to Co 3+ and the peaks at 782.26 eV and 797.7 eV correspond to Co 2+ of the h-MCO electrode.18,26 The two peaks at 786.66 eV and 803.15 eV are assigned to the ...
The growth of hierarchical morphologies of complex metal oxides directly onto the substrate is a challenging task. Here in we report, unique hollow-cuboidal MnCo 2 O 4 (h-MCO) morphology that offers insights into...
... Fig. 1C shows the survey spectrum of GO (red spectrum) and MCO@GO (green spectrum). displays the XPS spectrum of Mn 2p as seen in the peak at 642.4 eV and 654.2 eV corresponding to Mn 2p 1/2 and Mn 2p 3/2 is, which may split into four subpeaks, the two peaks are centered at the binding energy of 644.1 eV and 656.5 eV are attributed to Mn 2+ , while the other two peaks at 642.4 eV and 654.4 eV are ascribed to the Mn 3+ [43]. In the Co 2p spectrum Fig. 1E, the two major peaks located at 782.7 eV and 798.2 eV are related to Co 2p 3/2 and Co 2p 1/2 . ...
Hazardous 4-nitrophenol (4-NP) and its isomers are very harmful to humans, plants, and animals even at very low concentrations. Consequently, it is very urgent and essential to identify 4-NP in the environment with a simple and accurate method. Herein, MnCo2O4 (MCO) nanosphere was synthesized by simple co-precipitation process using sodium hydroxide as a precipitating agent and subsequent elimination by calcination. The [email protected] is prepared by ultrasound irradiation at room temperature. Graphene oxide was anchored with MCO nanospheres were performed excellent electrocatalytic activity owing to their Mn²⁺/Mn³⁺ and Co²⁺/Co³⁺ have an impressive synergistic effect (MCO) and large active surface area (GO). The prepared [email protected] nanocomposite was characterized by different analytical techniques namely XRD (crystal nature), FTIR (functional group), FESEM, TEM (morphological analysis), XPS (elemental state). The electrochemical characterization was monitored by CV and DPV. The [email protected] nanocomposite was drop cast on a glassy carbon electrode is referred to as [email protected]/GCE for the electrochemical determination of 4-NP with good practical applicability. The peak current was increased while increasing the concentration of 4-NP from 0.5 µM to 151.5 µM with a regression equation y=0.4952(µM)+3.092 and correlation coefficient R²=0.9921. From this slope value, the LOD and sensitivity were determined to be 0.012 µM and 6.868 μA μM–1 cm–2. The sensor was successfully used for practical application of the 4-NP determination in toxic tannery wastes with a strong agreement with the added value and the recovery results. The objective of our work has afforded to readers a thorough understanding of the synthesis and electrochemical sensing applications of [email protected] and some guidance in future research.
