Phase Stability of Nickel Hydroxides and Oxyhydroxides

Ven, Anton Van der; Morgan, Dane; Meng, Ying Shirley; Ceder, Gerbrand

doi:10.1149/1.2138572

Cited by 194 publications

(171 citation statements)

References 22 publications

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“…This has been attributed to changes between different phases of nickel hydroxide/oxyhydroxide (i.e., α-Ni(OH) 2 to β NiOOH or α-Ni(OH) 2 to γ-NiOOH. [36]. On the other hand, the cathodic wave at 0.3 V is similar to that obtained during the activation of massive nickel electrodes [37,38].…”

Section: Synthesis and Characterization Of The Electrocatalysts And Asupporting

confidence: 76%

“…showing the electrochemical response of the NiNP in a 1 M NaOH solution (Fig SI-1) exhibited the expected redox couples, which are associated to the nucleation of NiOOH and the formation of the pair Ni(OH) 2 /NiOOH [36]. It is interesting to note that the anodic peak potential shifted downwards by about 50 mV upon cycling.…”

Section: Synthesis and Characterization Of The Electrocatalysts And Amentioning

confidence: 87%

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Electrocatalytic activity of Ni-doped nanoporous carbons in the electrooxidation of propargyl alcohol

García‐Cruz

Sáez

Ania

et al. 2014

Carbon

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Please cite this article as: García-Cruz, L., Sáez, A., Ania, C.O., Solla-Gullón, J., Thiemann, T., Iniesta, J., Montiel, V., Electrocatalytic activity of Ni-doped nanoporous carbons in the electrooxidation of propargyl alcohol, Carbon (2014), doi: http://dx.doi.org/10.1016/j.carbon. 2014.02.066 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Ni-doped nanoporous carbons provided similar propargyl alcohol conversions for very low metallic contents. Nanoparticulated Ni on various carbon supports gave rise to the highest electrocatalytic activity in terms of product selectivity, with a clear dependence on Ni content. The results point to the importance of controlling the dispersion of the Ni phase within the carbon matrix for a full exploitation of the electroactive area of the metal. Additionally, a change in the mechanism of the propargyl alcohol electrooxidation was noted, which seems to be related to the physicochemical properties of the carbon support as well. Thus, the stereoselectivity of the electrooxidative reaction can be controlled by the active nickel content immobilized on the anode, with a preferential oxidation to (Z)-3-(2-propynoxy)-2-propenoic acid with high Ni-loading, and to propiolic acid with low loading of active Ni sites. Moreover, the formation of (E)-3-(2-propynoxy)-2-propenoic acid was discriminatory irrespective of the experimental conditions and Ni loadings on the carbon matrixes.

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Section: Synthesis and Characterization Of The Electrocatalysts And Asupporting

confidence: 76%

Section: Synthesis and Characterization Of The Electrocatalysts And Amentioning

confidence: 87%

Electrocatalytic activity of Ni-doped nanoporous carbons in the electrooxidation of propargyl alcohol

García‐Cruz

Sáez

Ania

et al. 2014

Carbon

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“…In β-and γ-NiOOH the distance between the Ni-O planes is over 4.6 Å, and in Ni(OH) 2 •xH 2 O it increases to 7.6 Å, as the water molecules enter the spaces between the protonated Ni-O layers. 28,75 These large lattice parameters seemingly argue against such crystal structures as models of the protonated material in our case; however, if only some of the Li + ions are replaced by H + ions, one can expect contraction rather than expansion, since the smaller proton would interact stronger with the oxygens and in this way more efficiently screen the repulsion between them.…”

Section: Discussion: H + /Li + Exchange Hypothesismentioning

confidence: 78%

“…28 Most authors, however, suggest that such cation exchange plays a minor role if any at all, favoring instead a redox process that is fully analogous to the one occurring in electrochemical delithiation. In this favored scenario, both Li + cations and oxygen atoms (referred to as "active oxygen species") 16,17 migrate toward the surface and combine with water and CO 2 to yield LiOH, LiHCO 3, and Li 2 CO 3, while Ni 3+ ions are reduced to Ni 2+ .…”

Section: LImentioning

confidence: 99%

Chemical Weathering of Layered Ni-Rich Oxide Electrode Materials: Evidence for Cation Exchange

Shkrob

Gilbert

Phillips

et al. 2017

J. Electrochem. Soc.

142

160

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Lithiated ternary oxides containing nickel, cobalt, and manganese are intercalation compounds that are used as positive electrodes in high-energy lithium-ion batteries. These oxides undergo changes, when they are stored in humid air or exposed to moisture, that adversely affect their electrochemical performance. There is a new urgency to better understanding of these "weathering" mechanisms as manufacturing moves toward a more environmentally benign aqueous processing of the positive electrode. Delithiation of the oxide and the formation of lithium salts (such as hydroxides and carbonates) coating the surface, are known to occur during moisture exposure. The redox reactions which follow this delithiation are believed to trigger all the other transformations. In this article we suggest another possibility: namely, the proton -lithium exchange. We argue that this hypothesis provides a simple, comprehensive rationale for our observations, which include contraction of the c-axis (unit cell) lattice parameter, rock salt phase formation in the subsurface regions, presence of amorphous surface films, and the partial recovery of oxide capacity during electrochemical relithiation. The detrimental effects of water exposure need to be mitigated before aqueous processing of the positive electrode can find widespread adoption during cell manufacturing. Improving the performance of lithium-ion batteries (LIBs) for electrically powered vehicles gives urgency to the development of high-capacity, high-voltage electrode materials, and layered Ni-rich oxides are presently among the most technological advanced materials that allow operation above +4.0 V vs Li + /Li. 1 Such materials (also known as NCMxyz materials) have the general composition of LiNi x/10 Co y/10 Mn z/10 O 2 , where x+y+z = 10. In these ternary oxides, the manganese stays in the Mn 4+ state during cell cycling, and the capacity mainly originates from the Ni 2+ /Ni 3+ and Ni 3+ /Ni 4+ redox couples. The monolayers of octahedra containing transition metal (TM) ions form a structural scaffold with the layers of mobile Li + ions placed in between. The crystalline material retains the structure of the progenitor material of the family, viz. α-LiCoO 2 , 2 with the unit cell belonging to the rhombohedral R(-3)m space group. During electrochemical cycling, the lithium ions intercalate into (and deintercalate from) the layered crystals as the redox state of (mainly the) nickel ions changes to provide the overall charge neutrality.In this study, we examine one such material, NCM523, which represents a particular trade-off between the cycling rate (that improves with Co content), safety (that improves with Mn content), and capacity (that increases with Ni content).1 The safety concerns mainly relate to the thermal and chemical stability, including oxidation of the organic electrolyte by catalytic centers at the oxide surface 3 and phase transitions in the delithiated material that occur when a significant fraction of nickel ions is reduced to Ni 2+ ions and molecular oxygen ...

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“…(NiOOH to Ni(OH) 2 ). During potential scanning in an alkaline solution, nickel can be oxidized to Ni(OH) 2 , which can occur in two crystallographic phases (i.e., a-Ni(OH) 2 and b-Ni(OH) 2 ) [15,16]. During scanning, a-Ni(OH) 2 forms first, and this phase is converted to the more stable bNi(OH) 2 with increasing time and potential.…”

Section: Resultsmentioning

confidence: 99%

Electrocatalytic oxidation of urea on a sintered Ni–Pt electrode

2016

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Urea is present in the environment as a result of large amounts of wastewater from various origins. One of the most effective methods for disposing of urea involves electrochemical oxidation. This study investigated the use of sintered Ni-Pt electrodes as anodes in the electrocatalytic oxidation of urea. The activity of the Ni-Pt electrodes was compared with those of conventional Ti/Pt and Ni electrodes. Based on our results, the sintered Ni-Pt electrodes exhibited much higher activity in the oxidation of urea compared with the conventional anodes.

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Phase Stability of Nickel Hydroxides and Oxyhydroxides

Cited by 194 publications

References 22 publications

Electrocatalytic activity of Ni-doped nanoporous carbons in the electrooxidation of propargyl alcohol

Electrocatalytic activity of Ni-doped nanoporous carbons in the electrooxidation of propargyl alcohol

Chemical Weathering of Layered Ni-Rich Oxide Electrode Materials: Evidence for Cation Exchange

Electrocatalytic oxidation of urea on a sintered Ni–Pt electrode

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