Characterization of the Nickel Cobaltite, NiCo2O4, Prepared by Several Methods: An XRD, XANES, EXAFS, and XPS Study

Marco, José F.; Gancedo, J. R.; Gracia, M.; Gautier, J.L.; Rı́os, E.; Berry, Frank J.

doi:10.1006/jssc.2000.8749

Cited by 662 publications

(334 citation statements)

References 30 publications

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“…As shown in Fig. 4c, Co is present in two oxidation states, i.e., Co 3+ (779.4 and 794.3 eV) and Co 2+ (780.7 and 795.8 eV) [38], and the two shake-up type peaks at 788 and 804 eV are satellite peaks for Co [39]. Interestingly, the Ir 4f emission spectrum shown in Fig.…”

Section: Resultsmentioning

confidence: 86%

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IrNi nanoparticle-decorated flower-shaped NiCo2O4 nanostructures: controllable synthesis and enhanced electrochemical activity for oxygen evolution reaction

et al. 2016

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In this work, we demonstrated the enhanced oxygen evolution reaction (OER) activity of flower-shaped cobalt-nickel oxide (NiCo2O4) decorated with iridium-nickel bimetal as an electrode material. The samples were prepared by carefully depositing pre-synthesized IrNi nanoparticles on the surfaces of the NiCo2O4 nano-flowers. Compared with bare NiCo2O4, IrNi, and IrNi/Co3O4, the IrNi/NiCo2O4 exhibited significantly enhanced electrocatalytic activity in the OER, including a lower overpotential of 210 mV and a higher current density at an overpotential of 540 mV. We found that the IrNi/NiCo2O4 showed more efficient electron transport behavior and reduced polarization because of its bimetal IrNi modification by analyzing its Tafel slope and turnover frequency. Furthermore, the electrocatalytic mechanism of IrNi/NiCo2O4 in the OER was studied, and it was found that the combined active sites of the composite effectively improved the rate determining step. The synergic effect of the bimetal and metal oxide plays an important role in this reaction, enhancing the transmission efficiency of electrons and providing more active sites for the OER. The results reveal that IrNi/NiCo2O4 is an excellent electrocatalyst for OER.

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Section: Resultsmentioning

confidence: 86%

“…The fitting peak of O2 at 531.1 eV indicates defects, contaminants, and a number of surface species [45]. Finally, the peak at 532.5 eV indicates minimum physical adsorbed and chemisorbed water on the material surface (O-H) [38,46] (0<x<1). The XPS spectra of the pure bimetallic alloy IrNi is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

IrNi nanoparticle-decorated flower-shaped NiCo2O4 nanostructures: controllable synthesis and enhanced electrochemical activity for oxygen evolution reaction

et al. 2016

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“…The high-resolution O1s XPS spectrum for the as-prepared PtCo 2 Ni 2 /C indicates the fitting peak at 531.5 eV associated with oxygen in -OH groups and the peak at 532.1 eV attributed to the physior chemisorbed water at the surface (Fig. S4) [47,48]. The high-resolution XPS spectra of Ni2p of Pt 2 CoNi show BE values at 852.0 and 869.4 eV, which correspond to metallic Ni.…”

Section: Lettersmentioning

confidence: 97%

Carbon-supported PtCo2Ni2 alloy with enhanced activity and stability for oxygen reduction

Gao

et al. 2015

Sci. China Mater.

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The commercialization of proton exchange membrane fuel cells (PEMFCs) is still restricted by the well-known dilemma, that is, the heavy dependence of using expensive plantinum (Pt) catalyst to negotiate the sluggish oxygen reduction reaction (ORR) kinetics in fuel cell cathodes. Here, a carbon-supported PtCo2Ni2 alloy catalyst with low Pt usage was synthesized via a simple method, which exhibited exceptional ORR activity with a more positive half-wave potential (E1/2) ~57 mV, which was more positive than the state-of-the-art Pt/C catalysts. Moreover, the alloy catalyst performs excellent durability after 10,000 harsh cycles compared with that of Pt/C catalyst in acidic solution, which may be developed as a promising alternative for Ptbased catalysts in fuel cell technology.Proton exchange membrane fuel cells (PEMFCs) have drawn intensive attention as promising candidates for nonpolluting and high-efficiency energy conversion in automotive and portable power [1−3]. However, large-scale commercialization of this technology is greatly hindered by the heavy dependence of using rare Pt as electrocatalysts [4−7]. Considerable efforts have been devoted to developing alternative Pt-free electrocatalysts, while Pt is still the most effective oxygen reduction reaction (ORR) catalyst, especially in acidic environment [8−14]. Therefore, to make PEMFCs economically competitive, an effective way is to develop composition and surface tunable Pt-based alloy catalysts with low cost, high activity and durability [15−20].Recently, a number of studies demonstrated that Ptbased multimetallic electrocatalysts (alloyed with Ni, Co, Fe, Cu, etc.) with altered surface electronic structure would exhibit high catalytic activity for the ORR [21−34]. Recently, our research on Pt-based binary and ternary electrocatalysts revealed that excellent catalytic activity for ORR, fo rmic acid oxidation, and methanol oxidation could be achieved by alloying Pt with other cheaper transition elements such as Pd, Ni, and Cu by taking advantages of the altered electronic structure of Pt and the favorable surface composition of the alloy electrocatalyst [18,21,24,35,36]. For instance, a mixed PtPd alloy surface could be obtained by surface atomic redistribution of ternary PtPdCu upon potential cycling in an acidic electrolyte, and the distinctive topmost layer played a key role in the enhancement of catalytic activity [35]. Moreover, we found that mixed-PtPdshell ternary PtPdCu nanoparticle nanotubes also showed significant enhancement for ORR by using copper nanowires as templates [18]. The c ore/shell Pd/PtFe catalysts also show improved ORR activity and durability, which is highly associated with the FePt shell thickness [37]. It is believed that the arrangement of composition of the topmost layer, and rationally introducing foreign metals to modify the electronic structure of Pt are critical factors to enhance the electrochemical performance of Pt-based ORR catalysts [38].On the other hand, carbon support technology has been verified to be an effective...

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“…This is a powerful method to characterize the chemical state and local structure of Fe and Ni atoms. [26][27][28][29][30] Figure 10 shows the X-ray absorption near-edge structure spectra at the (a) Fe and (b) Ni K absorption edges of the precursor with 34 at% Fe and RAFPs derived from the above precursor. Here, the normalized absorbance is plotted against the incident X-ray energy.…”

Section: Synthesis Of Fe-ni Alloy Ne Particles By Reductionannealingmentioning

confidence: 99%

Composition-Controlled Fe-Ni Alloy Fine Particles Synthesized by Reduction-Annealing of Polyol-Derived Fe-Ni Hydroxide

et al. 2016

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Fe-Ni hydroxide ne particles with a layered double hydroxide-type structure were precipitated as an intermediate in polyol (ethyleneglycol) solution with Fe compositions ranging between about 10 and 90 at%. Subsequent reduction-annealing of the above polyol-derived particles with 13-56 at% Fe at 673 K resulted in the synthesis of fcc Fe-Ni alloy ne particles with their sizes less than about 50 nm. The lattice constants of fcc Fe-Ni alloy particles were close to those of the bulk fcc Fe-Ni alloy with similar compositions. X-ray absorption spectroscopy measurements suggested that fcc Fe-Ni alloy was formed through simultaneous reduction of Fe and Ni in Fe-Ni hydroxide. Consequently, the reduction-annealing of polyol-derived Fe-Ni hydroxide ne particles is proved to be an effective process for obtaining composition-controlled Fe-Ni alloy ne particles.

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Characterization of the Nickel Cobaltite, NiCo2O4, Prepared by Several Methods: An XRD, XANES, EXAFS, and XPS Study

Cited by 662 publications

References 30 publications

IrNi nanoparticle-decorated flower-shaped NiCo2O4 nanostructures: controllable synthesis and enhanced electrochemical activity for oxygen evolution reaction

IrNi nanoparticle-decorated flower-shaped NiCo2O4 nanostructures: controllable synthesis and enhanced electrochemical activity for oxygen evolution reaction

Carbon-supported PtCo2Ni2 alloy with enhanced activity and stability for oxygen reduction

Composition-Controlled Fe-Ni Alloy Fine Particles Synthesized by Reduction-Annealing of Polyol-Derived Fe-Ni Hydroxide

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