Surface effects in the energy loss near edge structure of different cobalt oxides

Zhang, Zaoli

doi:10.1016/j.ultramic.2006.11.006

Cited by 41 publications

(35 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The decrease in height for the pre-peak in the sample after 2000 cycles indicates the formation of oxygen vacancies in conjunction with the decrease in valence state, as observed from Co L-edge and Ni L-edge. This result agrees with the previously reported results for similar CoO x materials [34,35]. The formation of oxygen vacancies and functional hydroxyl groups during long-term charge-discharge cycling is also validated by Xray photoelectron spectroscopy (XPS) (see Fig.…”

Section: Resultssupporting

confidence: 92%

Unveiling the Dynamic Capacitive Storage Mechanism of Co₃O₄@NiCo₂O₄ Hybrid Nanoelectrodes for Supercapacitor Applications

Li¹,

Zhang

Li³

et al. 2016

Meet. Abstr.

View full text Add to dashboard Cite

a b s t r a c tWe report a simple and cost-effective approach to the synthesis of hierarchical mesporous Co 3 O 4 @NiCo 2 O 4 nanoforests on Ni foam for supercapacitor (SC) electrode applications by a coupled one-step solution and annealing process. The synthesized electrode exhibits capacitive activation during charge-discharge cycling (from 0.73 F/cm 2 of the pristine state to the peak value of 1.12 F/cm 2 after 2000 cycles with only 1.8% loss compared to the peak capacitance after another 2000 cycles). We attribute such dynamic capacitive activation to (1) enlarged electroactive surface area through the formation of Co 3 O 4 @NiCo 2 O 4 core-shell structure and (2) enhanced electrical conductivity by forming oxygen vacancies and hydroxyl groups during charge-discharge cycling. Our findings provide a scientific explanation for the capacitive activation in cobalt oxide-binary nickel cobaltite compounds, and a new design guideline for the development of capacitive activation enabled, high performance transitional oxide electrodes.

show abstract

Section: Resultssupporting

confidence: 92%

Unveiling the Dynamic Capacitive Storage Mechanism of Co₃O₄@NiCo₂O₄ Hybrid Nanoelectrodes for Supercapacitor Applications

Li¹,

Zhang

Li³

et al. 2016

Meet. Abstr.

View full text Add to dashboard Cite

show abstract

“…However, a more detailed inspection revealed a slight difference in the ratios of the first and second O-K oxygen peaks (see the shadowed insert in Figure 6). As previously shown by Zhang [28], this decrease in the intensity of the O-K prepeak observed for Bi-Co3O4 was associated with a reduction in the number of Co-O bonds, leading to a more metallic character. In our system, we interpreted this as the gentle weakening of the Co-O bonding caused by the presence of bismuth cations on the catalyst surface.…”

Section: High-resolution Microscopy and Spectroscopysupporting

confidence: 76%

“…The spectra of the EELS analysis after the background subtraction and deconvolution with the use of the zero-loss peak are shown in the upper part of Figure 6. The spectra of both catalysts showed three overlapping peaks in the range of 530-550 eV, which matched well to the lattice oxygen of the cobalt spinel [28]. However, a more detailed inspection revealed a slight difference in the ratios of the first and second O-K oxygen peaks (see the shadowed insert in Figure 6).…”

Section: High-resolution Microscopy and Spectroscopymentioning

confidence: 71%

Atomic-Level Dispersion of Bismuth over Co3O4 Nanocrystals—Outstanding Promotional Effect in Catalytic DeN2O

et al. 2020

View full text Add to dashboard Cite

A series of cobalt spinel catalysts doped with bismuth in a broad range of 0–15.4 wt % was prepared by the co-precipitation method. The catalysts were thoroughly characterized by several physicochemical methods (X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), Raman spectroscopy (µRS), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption analyzed with Brunaer-Emmett-Teller theory (N2-BET), work function measurements (WF)), as well as aberration-corrected scanning transmission electron microscopy (STEM) coupled with energy-dispersive X-ray spectroscopy (EDX) and electron energy-loss spectroscopy (EELS). The optimal bismuth promoter content was found to be 6.6 wt %, which remarkably enhanced the performance of the cobalt spinel catalyst, shifting the N2O decomposition (deN2O) temperature window (T50%) down from approximately 400 °C (for Co3O4) to 240 °C (for the 6.6 wt % Bi-Co3O4 catalyst). The high-resolution STEM images revealed that the high activity of the 6.6 wt % Bi-Co3O4 catalyst can be associated with an even, atomic-level dispersion (3.5 at. nm−2) of bismuth over the surface of cobalt spinel nanocrystals. The improvement in catalytic activity was accompanied by an observed increase in the work function. We concluded that Bi promoted mostly the oxygen recombination step of a deN2O reaction, thus demonstrating for the first time the key role of the atomic-level dispersion of a surface promoter in deN2O reactions.

show abstract

“…In the low-temperature parent phase, LiCoMnO 4 , the O-K edge is characteristic of a spinel-type oxygen lattice, whereas in specimens quenched from higher temperatures, O-K edges resemble those of rock salt-type oxygen lattices [32]. Examples of these two extremes are shown in figure 11.…”

Section: Resultsmentioning

confidence: 99%

Spinel–rock salt transformation in LiCoMnO _{4−
δ}

et al. 2016

View full text Add to dashboard Cite

The transformation on heating LiCoMnO4, with a spinel structure, to LiCoMnO3, with a cation-disordered rock salt structure, accompanied by loss of 25% of the oxygen, has been followed using a combination of diffraction, microscopy and spectroscopy techniques. The transformation does not proceed by a topotactic mechanism, even though the spinel and rock salt phases have a similar, cubic close-packed oxygen sublattice. Instead, the transformation passes through two stages involving, first, precipitation of Li2MnO3, leaving behind a Li-deficient, Co-rich non-stoichiometric spinel and, second, rehomogenization of the two-phase assemblage, accompanied by additional oxygen loss, to give the homogeneous rock salt final product; a combination of electron energy loss spectroscopy and X-ray absorption near edge structure analyses showed oxidation states of Co2+ and Mn3+ in LiCoMnO3. Subsolidus phase diagram determination of the Li2O-CoOx-MnOy system has established the compositional extent of spinel solid solutions at approximately 500°C.

show abstract

Surface effects in the energy loss near edge structure of different cobalt oxides

Cited by 41 publications

References 24 publications

Unveiling the Dynamic Capacitive Storage Mechanism of Co₃O₄@NiCo₂O₄ Hybrid Nanoelectrodes for Supercapacitor Applications

Unveiling the Dynamic Capacitive Storage Mechanism of Co₃O₄@NiCo₂O₄ Hybrid Nanoelectrodes for Supercapacitor Applications

Atomic-Level Dispersion of Bismuth over Co3O4 Nanocrystals—Outstanding Promotional Effect in Catalytic DeN2O

Spinel–rock salt transformation in LiCoMnO _{4−
δ}

Contact Info

Product

Resources

About

Surface effects in the energy loss near edge structure of different cobalt oxides

Cited by 41 publications

References 24 publications

Unveiling the Dynamic Capacitive Storage Mechanism of Co3O4 @NiCo2O4 Hybrid Nanoelectrodes for Supercapacitor Applications

Unveiling the Dynamic Capacitive Storage Mechanism of Co3O4 @NiCo2O4 Hybrid Nanoelectrodes for Supercapacitor Applications

Atomic-Level Dispersion of Bismuth over Co3O4 Nanocrystals—Outstanding Promotional Effect in Catalytic DeN2O

Spinel–rock salt transformation in LiCoMnO 4− δ

Contact Info

Product

Resources

About

Unveiling the Dynamic Capacitive Storage Mechanism of Co₃O₄@NiCo₂O₄ Hybrid Nanoelectrodes for Supercapacitor Applications

Unveiling the Dynamic Capacitive Storage Mechanism of Co₃O₄@NiCo₂O₄ Hybrid Nanoelectrodes for Supercapacitor Applications

Spinel–rock salt transformation in LiCoMnO _{4−
δ}