The effect of firing temperature, preparation technique and composition on the electrical properties of the nickel cobalt oxide series NixCo1 - xOy

Lapham, Darren P.; Tseung, A. C. C.

doi:10.1023/b:jmsc.0000007751.14703.4b

Cited by 60 publications

(23 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Theoretically, CoNi (67:33) should form 100 wt% NiCo2O4 phase; however, it contains the mixture of 78 wt% NiCo2O4 phase and 22 wt% NiO phase based on the MAUD analysis. The formation of NiO phase orginates from the thermal decomposition of NiCo2O4 spinel phase above 400 °C during calcination process [38][39][40].…”

Section: Icp-aes and Bet Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Effect of Co/Ni ratios in cobalt nickel mixed oxide catalysts on methane combustion

Lim

Cho

Yang

et al. 2015

Applied Catalysis A: General

View full text Add to dashboard Cite

2Graphical abstract Highlights 1. Co-Ni mixed oxide having the ratios of Co to Ni of (50:50) exhibits the highest activity among the known transition metal oxide catalysts.2. Co-Ni mixed oxides having the ratios of Co to Ni of (50:50) show the highest activity for methane combustion.3. Distorted NiCo2O4 spinel structure plays a key role as the active sites for methane combustion.3 Abstract A series of cobalt nickel mixed oxide catalysts with the varying ratios of Co to Ni, prepared by co-precipitation method, were applied to methane combustion. Among the various ratios, cobalt nickel mixed oxides having the ratios of Co to Ni of (50:50) and (67:33) demonstrate the highest activity for methane combustion. Structural analysis obtained from X-Ray Diffraction (XRD) and Extended X-ray Absorption Fine Structure (EXAFS) evidently demonstrates that CoNi (50:50) and (67:33) samples consist of NiCo2O4 and NiO phase and, more importantly, NiCo2O4 spinel structure is largely distorted, which is attributed to the insertion of Ni 2+ ions into octahedral sites in Co3O4 spinel structure. Such structural disorder results in the enhanced portion of surface oxygen species, thus leading to the improved reducibility of the catalysts in the low temperature region as evidenced by temperature programmed reduction by hydrogen (H2 TPR) and X-ray Photoelectron Spectroscopy (XPS) O 1s results. They prove that structural disorder in cobalt nickel mixed oxides enhances the catalytic performance for methane combustion. Thus, it is concluded that a strong relationship between structural property and activity in cobalt nickel mixed oxide for methane combustion exists and, more importantly, distorted NiCo2O4 spinel structure is found to be an active site for methane combustion.

show abstract

Section: Icp-aes and Bet Resultsmentioning

confidence: 99%

“…It implies that decrement in activity can be caused by the surface coverage of NiCo2O4 by NiO phase, indicating that surface area decreases when NiO phase is dominant [39]. Increasing order of activity is as follows: NiO phase < Co3O4 phase < NiCo2O4 phase < distorted NiCo2O4 phase.…”

Section: Methane Combustion Activitymentioning

confidence: 99%

Effect of Co/Ni ratios in cobalt nickel mixed oxide catalysts on methane combustion

Lim

Cho

Yang

et al. 2015

Applied Catalysis A: General

View full text Add to dashboard Cite

show abstract

“…Theoretically, no NiO should exist but NiCo 2 O 4 if the Co/Ni ratio of the cobalt–nickel mixed oxides is more than 2:1. However, the NiO phase would form from the thermal decomposition of NiCo 2 O 4 spinel phase above 400 °C during calcination . According to the methane conversion over Co x Ni y catalysts in Figure , we know that catalysts of the former (Co1Ni4, Co1Ni2, Co1Ni1) have a higher catalytic activity than the Co2Ni1 and Co4Ni1 samples (e, f).…”

Section: Resultsmentioning

confidence: 99%

Low Temperature Complete Combustion of Lean Methane over Cobalt–Nickel Mixed‐Oxide Catalysts

Shao

Lin

et al. 2016

Energy Tech

View full text Add to dashboard Cite

Cobalt–nickel mixed oxides with different Co/Ni molar ratios were prepared by co‐precipitation and used for the catalytic combustion of lean methane. The catalytic performances for methane combustion were evaluated at steady‐state conditions at temperatures ranging from 250 to 500 °C, which were increased in step sizes of 25 °C. Among the catalysts, the cobalt–nickel mixed‐oxide catalysts with an appropriate Co/Ni ratio exhibit a high catalytic performance for the lean methane combustion, with the catalyst having a Co/Ni molar ratio of 1:4 showing the highest catalytic activity (methane conversion reached 100 % at 425 °C). On the basis of TEM and XRD results, the nanoparticles of the catalysts have a suitable interparticle spacing and more crystal defects. X‐ray photoelectron spectroscopy (XPS) results reveal a high number of surface‐active oxygen species and appropriate aliovalent cobalt ion numbers in the catalysts for high catalytic activity. All these effects contribute to the outstanding performance of these catalysts in the combustion of lean methane at low temperatures.

show abstract

“…A large number of methods have been reported for the synthesis of nanostructured materials into different forms. Oxides in nickel-cobalt system were prepared by various researchers using co-precipitation, cryochemical, spray pyrolysis, thermal decomposition, sol-gel, electrochemical deposition, chemical bath deposition and others [9,[45][46][47][48][49][50][51][52][53]. Thermal treatment of coprecipitated precursors is proven to be the most promising method in preparing cobaltite spinels [52].…”

Section: Introductionmentioning

confidence: 99%

“…Higher calcination temperature; for example 700°C is unfavourable for the formation of NiCo 2 O 4 phase as the sample starts to decompose to NiO and Co 3 O 4 . This indicates that low reaction temperature is required to prepare pure phase NiCo 2 O 4 as this spinel oxide has low thermal stability[9,64].Figure 2represents the XRD patterns of samples with calcination process conducted at different time duration. It is observed that the heating duration plays a major role in the formation of this spinel oxide.…”

mentioning

confidence: 99%

Synthesis and electrochemical properties of nanostructured nickel-cobalt oxides as supercapacitor electrodes in aqueous media

Chang

Zainal

Tan

et al. 2015

Int. J. Energy Res.

View full text Add to dashboard Cite

SummaryCo‐precipitation method was adopted in the preparation of nickel–cobalt oxides for potential application in supercapacitors. The formation of spinel nickel–cobalt oxide, NiCo2O4 started below 400 °C as confirmed by X‐ray diffraction analysis. Pure phase nickel cobaltite with cation ratio of 1:2 (Ni:Co) was obtained at calcination temperature of 400 °C. The spinel phase decomposed gradually until 700 °C. The calcination time for the formation of NiCo2O4 was found to be between 2 to 4 h. The particle size of the prepared sample studied by transmission electron microscopy showed a value of 9.47 nm. The electrochemical properties of the metal oxide were measured in various acidic, neutral and alkaline electrolyte systems (1.0 M HCl, 1.0 M KCl and 1.0 M KOH) by employment of cyclic voltammetry, galvanostatic charge–discharge test and electrochemical impedance spectroscopy. Ideal capacitor behaviour with the largest operating voltage of 1.0 V and good electrochemical stability were observed in NiCo2O4 using neutral KCl aqueous electrolyte. Meanwhile, the prepared sample displayed the highest surface redox activity in 1.0 M KOH alkaline electrolyte but showed the lowest electrochemical performance in acidic electrolyte. At the current density of 0.5 A g−1, 1.0 M HCl, 1.0 M KCl and 1.0 M KOH gave specific capacitance values of 3.8, 41.9 and 249.8 F g−1 respectively. Copyright © 2015 John Wiley & Sons, Ltd.

show abstract

The effect of firing temperature, preparation technique and composition on the electrical properties of the nickel cobalt oxide series Ni_xCo_{1 - x}O_y

Cited by 60 publications

References 28 publications

Effect of Co/Ni ratios in cobalt nickel mixed oxide catalysts on methane combustion

Effect of Co/Ni ratios in cobalt nickel mixed oxide catalysts on methane combustion

Low Temperature Complete Combustion of Lean Methane over Cobalt–Nickel Mixed‐Oxide Catalysts

Synthesis and electrochemical properties of nanostructured nickel-cobalt oxides as supercapacitor electrodes in aqueous media

Contact Info

Product

Resources

About