Enhanced supercapacitive performances of hierarchical porous nanostructure assembled from ultrathin MnO2 nanoflakes

Dubal, Deepak P.; Holze, Rudolf; Kulal, Prakash

doi:10.1007/s10853-012-6783-6

Cited by 30 publications

(25 citation statements)

References 25 publications

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“…3 Furthermore, a-MnO 2 has been demonstrated to deliver high capacitance as a supercapacitor electrode, particularly in nanostructured form. 4,5 In both technologies the good performance is directly connected to the surface properties of a-MnO 2 , but despite this the structures and defect formation remain poorly characterised. With a clear motivation to better understand the performance of this material in catalytic and supercapacitor applications, in this work we apply density functional theory (DFT) simulations to understand surface phenomena in this promising material.…”

Section: Introductionmentioning

confidence: 99%

Surface properties of α-MnO₂: relevance to catalytic and supercapacitor behaviour

2014

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Hollandite (a-)MnO 2 gives superior performance compared to other MnO 2 polymorphs in surface sensitive applications in supercapacitors and catalysis. However, a thorough understanding of its atomic-scale surface properties is lacking, which we address here using density functional theory (DFT). A Wulff construction based upon relaxed surface energies demonstrates that the equilibrium morphology expresses the low index (100), (110) and (111) surfaces as well as the high index (211) and (112) surfaces.The predicted morphology exhibits clear elongation along the c-axis which is consistent with the large number of nanorod type structures that are obtainable experimentally. The surface structures expressed in the morphology are discussed in detail and it is found that a-MnO 2 gives rise to larger surface relaxations than are observed for the less open rutile structured MnO 2 . Enhanced magnetic moments at surface sites are rationalised by a crystal field argument. Experimental studies consistently find that a-MnO 2 has higher catalytic activity than other polymorphs of MnO 2 . In this work, calculated formation energies for oxygen vacancy defects at the expressed surfaces are demonstrably lower, by $1 eV, than for rutile MnO 2 surfaces [Tompsett et al., JACS, 2014, 136, 1418. The lowest vacancy formation energy occurs at the (112) surface, which despite its relative high Miller index constitutes 17% of the surface area of the calculated morphology. This may play a key role in the favourable catalytic performance observed for a-MnO 2 in a broad range of applications.

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Section: Introductionmentioning

confidence: 99%

Surface properties of α-MnO₂: relevance to catalytic and supercapacitor behaviour

2014

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“…7 describes the cycle performance, and the coulombic efficiency of the amorphous MnO 2 film at current 0.82 A g À1 for 200 cycles using constant current galvanostatic charge-discharge technique and the inset shows the charge-discharge curves for initial 5 cycles. The discharge specific capacitance is 360 F g À1 for the first cycle, which is better than most of the results reported in literature [25,30,32]. The discharge specific capacitance retention is about 92.7% after 200 cycles with coulombic efficiency ranging from 99.5 to 100%.…”

Section: Resultsmentioning

confidence: 48%

“…There are two process of formation of films on the stainless steel substrates: nucleation and particle growth and the film formation mechanism has been described elsewhere [25]. The reaction of formation of MnO 2 can be written as,…”

Section: Resultsmentioning

confidence: 99%

“…In this context manganese oxides are the most promising materials due to its low cost, environment friendly in nature and excellent performance [20][21][22]. Manganese oxide films have been prepared by different methods including sol-gel method [23][24][25][26][27][28][29], electrochemical deposition method [30][31][32], and physical vapor deposition method [33][34][35] etc. The values of specific capacitance of manganese oxide film are reported as 240 F g À1 [30], 243.2 F g À1 [32], 328 F g À1 [25], etc.…”

Section: Introductionmentioning

confidence: 99%

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Sol-gel synthesis of manganese oxide films and their predominant electrochemical properties

Sarkar

Satpati

Kumar

et al. 2015

Electrochimica Acta

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“…Dubal et al [28] prepared α-MnO 2 through the CBD method and obtained specific capacitance is 328 F g -1 in a potential window of -0.1 -0.9 V/SCE. Among these, CBD is less investigated as far as dealing with MnO 2.…”

Section: Introductionmentioning

confidence: 99%

Alcohol mediated growth of α-MnO₂thin films from KMnO₄precursor for high performance supercapacitors

et al. 2014

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AbstractsThe energy storage devices, with low cost, high energy density, high power density and long cycle life, have prime importance in order to solve the problem of interrupted power supply of the renewable generation systems. In present work, MnO 2 thin films have been deposited by simple, scalable, additive-free, binder-less, low cost, low temperature and eco-friendly chemical bath deposition method. The impact of three different alcohols (methanol, ethanol, 2-propenol), as a reducing agent, on the morphological, structural and electrochemical properties of MnO 2 thin film is investigated. The MnO 2 thin film prepared with the methanol as a reducing agent exhibits high specific surface area with excellent electrochemical features such as, high specific capacitance of 633 F g -1 and high energy density of 65.9 W h kg -1 at current density of 1 mA cm -2 along with a good cycling stability of 95% after 2000 of CV cycles. Such beating electrochemical properties suggest that MnO 2 thin film prepared with the methanol as a reducing agent using chemical bath deposition is a significant method to prepare reliable electrode material for future energy storage devices.

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Enhanced supercapacitive performances of hierarchical porous nanostructure assembled from ultrathin MnO2 nanoflakes

Cited by 30 publications

References 25 publications

Surface properties of α-MnO₂: relevance to catalytic and supercapacitor behaviour

Surface properties of α-MnO₂: relevance to catalytic and supercapacitor behaviour

Sol-gel synthesis of manganese oxide films and their predominant electrochemical properties

Alcohol mediated growth of α-MnO₂thin films from KMnO₄precursor for high performance supercapacitors

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Enhanced supercapacitive performances of hierarchical porous nanostructure assembled from ultrathin MnO2 nanoflakes

Cited by 30 publications

References 25 publications

Surface properties of α-MnO2: relevance to catalytic and supercapacitor behaviour

Surface properties of α-MnO2: relevance to catalytic and supercapacitor behaviour

Sol-gel synthesis of manganese oxide films and their predominant electrochemical properties

Alcohol mediated growth of α-MnO2thin films from KMnO4precursor for high performance supercapacitors

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Product

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Surface properties of α-MnO₂: relevance to catalytic and supercapacitor behaviour

Surface properties of α-MnO₂: relevance to catalytic and supercapacitor behaviour

Alcohol mediated growth of α-MnO₂thin films from KMnO₄precursor for high performance supercapacitors