Effect of alkali and alkaline earth metal dopants on catalytic activity of mesoporous cobalt oxide evaluated using a model reaction

Bingwa, Ndzondelelo; Bewana, Semakaleng; Ndolomingo, Matumuene Joe; Mawila, Naphtaly; Mogudi, Batsile M.; Ncube, Phendukani; Carleschi, Emanuela; Doyle, Bryan P.; Haumann, Marco; Meijboom, Reinout

doi:10.1016/j.apcata.2018.01.028

Cited by 15 publications

(8 citation statements)

References 31 publications

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“…These two components can be ascribed to the Co 3+ (BE 2p 3/2 = 780.35 eV), which accounts for roughly two-thirds of the spectral weight (taking into account the potential error associated with the choice of background for the fit) and Co 2+ oxidation states (BE 2p 3/2 = 782.27 eV), which accounts for the other one-third of the spectral weight. Similarly, for Mn 0.5 Ni 0.5 Co 2 O 4 /C, the BE for Co 3+ 2p 3/2 (66% of the spectral weight) is 780.02 eV, while that of Co 2+ 2p 3/2 (34%) is 781.94 eV, which is consistent with the relevant literature on Co 3 O 4 -type compounds [47,48]. The Co 2p core-level line shape shows that Co is very robust towards the Mn-to-Ni substitution.…”

Section: Physicochemical Characterizationsupporting

confidence: 88%

“…4b,c. This BE region is divided into two main regions, that is,~777-792 eV for Co 2p 3/2 and~792-807 eV for Co 2p 1/2 [45,46], and this is consistent with the line shape of the mixed-valent Co 3 O 4 where Co ions have both Co 3+ and Co 2+ oxidation states [47,48]. For example, the fit to the x = 1 sample is shown at the bottom of Figure 4b for the entire series.…”

Section: Physicochemical Characterizationsupporting

confidence: 64%

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Mn-Ni-Co-O Spinel Oxides towards Oxygen Reduction Reaction in Alkaline Medium: Mn0.5Ni0.5Co2O4/C Synergism and Cooperation

et al. 2021

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Mn-doped spinel oxides MnxNi1−xCo2O4 (x = 0, 0.3, 0.5, 0.7, and 1) were synthesized using the citric acid-assisted sol–gel method. The Mn0.5Ni0.5Co2O4 (x = 0.5) supported on carbon nanosheets, Mn0.5Ni0.5Co2O4/C, was also prepared using the same method employing NaCl and glucose as a template and carbon source, respectively, followed by pyrolysis under an inert atmosphere. The electrocatalytic oxygen reduction reaction (ORR) activity was performed in alkaline media. Cyclic voltammetry (CV) was used to investigate the oxygen reduction performance of MnxNi1−xCo2O4 (x = 0, 0.3, 0.5, 0.7, and 1), and Mn0.5Ni0.5Co2O4 was found to be the best-performing electrocatalyst. Upon supporting the Mn0.5Ni0.5Co2O4 on a carbon sheet, the electrocatalytic activity was significantly enhanced owing to its large surface area and the improved charge transfer brought about by the carbon support. Rotating disk electrode studies show that the ORR electrocatalytic activity of Mn0.5Ni0.5Co2O4/C proceeds via a four-electron pathway. Mn0.5Ni0.5Co2O4/C was found to possess E1/2(V) = 0.856, a current density of 5.54 mA cm−2, and a current loss of approximately 0.11% after 405 voltammetric scan cycles. This study suggests that the interesting electrocatalytic performance of multimetallic transition metal oxides can be further enhanced by supporting them on conductive carbon materials, which improve charge transfer and provide a more active surface area.

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Section: Physicochemical Characterizationsupporting

confidence: 88%

Section: Physicochemical Characterizationsupporting

confidence: 64%

Mn-Ni-Co-O Spinel Oxides towards Oxygen Reduction Reaction in Alkaline Medium: Mn0.5Ni0.5Co2O4/C Synergism and Cooperation

et al. 2021

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“…Its normalised Co 2p core level was therefore subtracted from that of the other two samples to give the different spectras "CSCF3-CSCF1" and "CSCF2-CSCF1" displayed in the bottom part of Figure 4b as blue and red open circles, respectively. Their line shape was fitted with two spin-orbit doublets, ascribed to Co 2 + and Co 3 + oxidation states, for the main peaks and one for the high BE satellite [70,71]. The overall fit is found to superimpose well with the experimental data and confirms the difference in the line shape between the two spectra.…”

Section: Xps Analysissupporting

confidence: 57%

Ce_0.8Sr_0.2Co_xFe_1‐xO_3‐δ (x=0.2, 0.5, 0.8) – A Perovskite‐type Nanocomposite for Application in the Oxygen Evolution Reaction in Alkaline Media

et al. 2020

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Three perovskite-type nanocomposites, i. e. Ce 0.8 Sr 0.2 Co x Fe 1-x O 3-δ (x = 0.2, CSCF1; 0.5, CSCF2; 0.8, CSCF3), were synthesized employing the sol-gel technique, subsequent to which they were physically and electrochemically evaluated for their electrocatalytic activity towards the oxygen evolution reaction (OER) in alkaline medium (0.1 M KOH) at room temperature (25°C). Electrochemical characterisation revealed Ce 0.8 Sr 0.2 Co 0.8 Fe 0.2 O 3-δ (CSCF3) to be the most active having the lowest overpotential at 10 mA cm À 2 (440 mV), the lowest Tafel slope (40.7 mV dec À 1), the highest mass activity (20.11 mA mg À 1) and highest specific activity (2.22 mA cm À 2).

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“…For both CoCr 2 O 4 thin filmsspectra (a) and (c) in Fig. 13 the line shape of the Co 2p core level resembles that of Co 3 O 4 [44,45]. The intensity maxima for 2p 3/2 and 2p 1/2 are located at 780 eV and 795…”

Section: The Xrd Patterns Of Thementioning

confidence: 82%

Role of Ni substitution on structural, magnetic and electronic properties of epitaxial CoCr₂O₄ spinel thin films

Mohanty¹,

Chowdhury²,

Choudhary³

et al. 2020

Nanotechnology

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Cubic spinel CoCr 2 O 4 has attained recent attention due to its multiferroic properties. However, the Co site substitution effect on the structural and magnetic properties has rarely been studied in thin film form. In this work, the structural and magnetic properties of Co 1x Ni x Cr 2 O 4 (x = 0, 0.5) epitaxial thin films deposited on MgAl 2 O 4 (100) and MgO (100) substrates to manipulate the nature of strain in the films using pulsed laser deposition (PLD) technique are presented. The epitaxial nature of the films was confirmed through X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS) measurements. Raman measurements revealed a disappearance of characteristic A 1g and F 2g modes of the CoCr 2 O 4 with increase in the Ni content. Atomic force microscopy (AFM) studies show a modification of the surface morphology upon Ni substitution. Magnetic measurements disclose that the ferrimagnetic Curie temperature (T c ) of the CoCr 2 O 4 in thin film grown on MgAl 2 O 4 (100) and MgO (100) substrates were found to be 100.6 ± 0.5 K and 93.8 ± 0.2 K, respectively. With Ni substitution the transition temperatures significantly get enhanced from that of CoCr 2 O 4 . X-ray photoelectron spectroscopy (XPS) suggests Cr 3+ oxidation states in the films, while Co ions are present in a mixed Co 2+ /Co 3+ oxidation state. The substitution of Ni at Co site significantly modifies the line shape of the core level as well as the valence band. Ni ions are also found to be in a mixed 2+/3+ oxidation state. O 1s core level display asymmetry related to possible defects like oxygen vacancies in the films. CoCr 2 O 4 is a ferrimagnetic spinel compound with complex magnetic interactions at low temperatures [1]. The magnetic cations Co 2+ and Cr 3+ ions occupy the tetrahedral A and octahedral B sites, respectively, of the spinel structure [1]. Below Curie temperature (T C = 93 K), a collinear ferrimagnetic ordering occurs, with further lowering the temperature to 26 K (T S ) the compound develops a short-range-ordered (SRO) spiral component [1]. Theoretical calculations has also evidenced the T S feature due to the nesting of the Fermi surface having high degree of magnetic instability in the system associated with the nesting vector q along the [110] direction [2]. Recent experiments have shown the size dependence of these magnetic transitions [3]. Below a critical particle size of d c , spiral = 4.4 (1) nm, the spiral ordering vanishes [3] and for size less than d c , col = 3.3 (1) nm, the collinear magnetic order disappears [3]. A lock-in transition at a temperature T L = 15 K appears because of the incommensurate-to-commensurate magnetic phase transition [1]. At T L the period of the spin spiral eventually "locks in" to the lattice parameter [1]. This spiral component is responsible for inducing the multiferroicity in CoCr 2 O 4 [1]. Structurally, CoCr 2 O 4 is stable and remains cubic with space group Fd ̅ m at all temperatures as the sample is cooled down to 10 K [4].On the other hand for NiCr 2 O 4 the crystal ...

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Effect of alkali and alkaline earth metal dopants on catalytic activity of mesoporous cobalt oxide evaluated using a model reaction

Cited by 15 publications

References 31 publications

Mn-Ni-Co-O Spinel Oxides towards Oxygen Reduction Reaction in Alkaline Medium: Mn0.5Ni0.5Co2O4/C Synergism and Cooperation

Mn-Ni-Co-O Spinel Oxides towards Oxygen Reduction Reaction in Alkaline Medium: Mn0.5Ni0.5Co2O4/C Synergism and Cooperation

Ce_0.8Sr_0.2Co_xFe_1‐xO_3‐δ (x=0.2, 0.5, 0.8) – A Perovskite‐type Nanocomposite for Application in the Oxygen Evolution Reaction in Alkaline Media

Role of Ni substitution on structural, magnetic and electronic properties of epitaxial CoCr₂O₄ spinel thin films

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Effect of alkali and alkaline earth metal dopants on catalytic activity of mesoporous cobalt oxide evaluated using a model reaction

Cited by 15 publications

References 31 publications

Mn-Ni-Co-O Spinel Oxides towards Oxygen Reduction Reaction in Alkaline Medium: Mn0.5Ni0.5Co2O4/C Synergism and Cooperation

Mn-Ni-Co-O Spinel Oxides towards Oxygen Reduction Reaction in Alkaline Medium: Mn0.5Ni0.5Co2O4/C Synergism and Cooperation

Ce0.8Sr0.2CoxFe1‐xO3‐δ (x=0.2, 0.5, 0.8) – A Perovskite‐type Nanocomposite for Application in the Oxygen Evolution Reaction in Alkaline Media

Role of Ni substitution on structural, magnetic and electronic properties of epitaxial CoCr2O4 spinel thin films

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Ce_0.8Sr_0.2Co_xFe_1‐xO_3‐δ (x=0.2, 0.5, 0.8) – A Perovskite‐type Nanocomposite for Application in the Oxygen Evolution Reaction in Alkaline Media

Role of Ni substitution on structural, magnetic and electronic properties of epitaxial CoCr₂O₄ spinel thin films