The effect of pH and anions on the anisotropic growth of MnO2

Ji, Zhonghai; Dong, Bin; Liu, Yunqi; Liu, Chenguang

doi:10.1016/j.materresbull.2012.07.020

Cited by 4 publications

(2 citation statements)

References 25 publications

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“…The shape may be described as being like a short pencil that has been sharpened at both ends. The tendency toward an elongated rod-like structure may be important to the nanorod and nanotube-type − morphologies of rutile MnO 2 that have shown promising electrochemical performance as battery cathodes, oxygen reduction catalysts, , and supercapacitors . By considering higher Miller indexes than treated in previous computational studies, we bring to light the importance of new surfaces of importance to the properties of this system.…”

Section: Resultsmentioning

confidence: 89%

Rutile (β-)MnO₂ Surfaces and Vacancy Formation for High Electrochemical and Catalytic Performance

2014

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MnO 2 is a technologically important material for energy storage and catalysis. Recent investigations have demonstrated the success of nanostructuring for improving the performance of rutile MnO 2 in Li-ion batteries and supercapacitors and as a catalyst. Motivated by this we have investigated the stability and electronic structure of rutile (β-)MnO 2 surfaces using density functional theory. A Wulff construction from relaxed surface energies indicates a rod-like equilibrium morphology that is elongated along the c-axis, and is consistent with the large number of nanowire-type structures that are obtainable experimentally. The (110) surface dominates the crystallite surface area. Moreover, higher index surfaces than considered in previous work, for instance the (211) and (311) surfaces, are also expressed to cap the rod-like morphology. Broken coordinations at the surface result in enhanced magnetic moments at Mn sites that may play a role in catalytic activity. The calculated formation energies of oxygen vacancy defects and Mn reduction at key surfaces indicate facile formation at surfaces expressed in the equilibrium morphology. The formation energies are considerably lower than for comparable structures such as rutile TiO 2 and are likely to be important to the high catalytic activity of rutile MnO 2 . ■ INTRODUCTIONEnergy storage for hybrid electric vehicles and renewable energy sources is a pressing technological challenge for which Li-ion batteries and supercapacitors are key candidate systems. The conventional Li-ion intercalation cathode, LiCoO 2 , faces challenges of toxicity and high cost. Current supercapacitors based on carbon cathodes are limited by their storage capacity. The demand for higher capacity and higher power energy storage has led to a surge in interest in nanostructured electrodes. 1 Nanostructuring has been shown to improve the energy storage properties of rutile MnO 2 for both Li-ion batteries 2,3 and supercapacitors. 4−6 However, the mechanisms for this improvement are not fully understood on the atomic-scale. In addition to its role as an electrode material, nanostructured rutile MnO 2 has been shown to give good performance as a catalyst, 7 with much recent interest in its potential role in the Li−O 2 battery. 8 Knowledge of the surface features of rutile MnO 2 at the atomic and electronic level would provide valuable information regarding its energy storage and catalytic mechanisms. With the clear impetus to better understand the performance of rutile MnO 2 in three technologies, Li-ion batteries, supercapacitors and catalysis, in this work we apply first-principles simulations to understand surface phenomena in this promising material.Rutile MnO 2 is the subject of extensive research for its applications in Li-ion batteries, but early work indicated that bulk samples did not allow significant Li-ion intercalation. 2,9,10

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Section: Resultsmentioning

confidence: 89%

Rutile (β-)MnO₂ Surfaces and Vacancy Formation for High Electrochemical and Catalytic Performance

2014

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“…However, dissolution-recrystallization cycles are not only triggered by temperature, but are also caused by reaction conditions, such as pH, size difference, form stability, etc. [59][60][61][62] On adjusting the pH of the hydrothermal reaction for the synthesis of α-Fe 2 O 3 micro-crystals during the dissolution-recrystallization process, the shape of the α-Fe 2 O 3 micro-crystals sequentially evolved from the initial nanospindles of the sacrificial template β-FeOOH to American football-shaped, angular American football-shaped and cubic after 2 h crystallization time. 63 Although the crystal quality is controlled by dissolution-recrystallization cycles, the triggering parameters are pH, size and form rather than temperature.…”

Section: The Basic Protocol Of Temperature Cycling During Crystalliza...mentioning

confidence: 99%

Application of temperature cycling for crystal quality control during crystallization

Yang

2016

CrystEngComm

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Characteristics of crystal quality, including crystal size distribution, size, morphology, polymorphism and chirality, have been established as important indicators of crystalline materials. There have been many attempts at controlling crystal quality during crystallization. Herein, this study summarizes crystal quality control by using temperature cycling during solution state crystallization. During crystallization, the temperature cycling is implemented through successive heating-cooling cycles for dissolution and recrystallization in crystal suspension. Therefore, the fines crystals or one species are expected to dissolve out completely during the heating period, and the remaining crystals or dominant species continuously grow or nucleate during the cooling period. When such temperature cycling is facilitated during crystallization, the characteristics of crystal quality, including crystal size distribution, size, morphology, polymorphism and chirality, are well managed. Furthermore, based on the basic principle of temperature cycling, the key parameters for controlling each characteristic of crystal quality are clearly elucidated during the process. Thus, this review provides qualitative insight into the general operation strategies and the principle of temperature cycling for crystal quality control during crystallization.

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Effect of pH on morphology and supercapacitive properties of manganese oxide/polypyrrole nanocomposite

Gan

Lim

Huang

et al. 2015

Applied Surface Science

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The effect of pH and anions on the anisotropic growth of MnO2

Cited by 4 publications

References 25 publications

Rutile (β-)MnO₂ Surfaces and Vacancy Formation for High Electrochemical and Catalytic Performance

Rutile (β-)MnO₂ Surfaces and Vacancy Formation for High Electrochemical and Catalytic Performance

Application of temperature cycling for crystal quality control during crystallization

Effect of pH on morphology and supercapacitive properties of manganese oxide/polypyrrole nanocomposite

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The effect of pH and anions on the anisotropic growth of MnO2

Cited by 4 publications

References 25 publications

Rutile (β-)MnO2 Surfaces and Vacancy Formation for High Electrochemical and Catalytic Performance

Rutile (β-)MnO2 Surfaces and Vacancy Formation for High Electrochemical and Catalytic Performance

Application of temperature cycling for crystal quality control during crystallization

Effect of pH on morphology and supercapacitive properties of manganese oxide/polypyrrole nanocomposite

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Product

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Rutile (β-)MnO₂ Surfaces and Vacancy Formation for High Electrochemical and Catalytic Performance

Rutile (β-)MnO₂ Surfaces and Vacancy Formation for High Electrochemical and Catalytic Performance