Can Faradaic Processes in Residual Iron Catalyst Help Overcome Intrinsic EDLC Limits of Carbon Nanotubes?

Emmett, Robert K.; Karakaya, Mehmet; Podila, Ramakrishna; Arcila-Velez, Margarita R.; Zhu, Jingyi; Rao, Apparao M.; Roberts, Mark

doi:10.1021/jp5097184

Cited by 16 publications

(18 citation statements)

References 24 publications

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“…For example, the free standing buckypaper electrodes were utilised to improve the energy capacity [49], electrode strength [40] and scalable production of the electrode materials [44]. An interesting study shows that CNTs can be ruptured by voltammetric cycling the CNTs electrode beyond the electrolysis limit in acid solution, where the residual catalyst nanoparticles in the CNT were then exposed [49].…”

Section: Cnt-poapmentioning

confidence: 99%

Redox electrode materials for supercapatteries

Chen

2016

Journal of Power Sources

207

111

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Redox electrode materials, including transition metal oxides and electronically conducting polymers, are capable of faradaic charge transfer reactions, and play important roles in most electrochemical energy storage devices, such as supercapacitor, battery and supercapattery. Batteries are often based on redox materials with low power capability and safety concerns in some cases. Supercapacitors, particularly those based on redox inactive materials, e.g. activated carbon, can offer high power output, but have relatively low energy capacity. Combining the merits of supercapacitor and battery into a hybrid, the supercapattery can possess energy as much as the battery and output a power almost as high as the supercapacitor. Redox electrode materials are essential in the supercapattery design. However, it is hard to utilise these materials easily because of their intrinsic characteristics, such as the low conductivity of metal oxides and the poor mechanical strength of conducting polymers. This article offers a brief introduction of redox electrode materials, the basics of supercapattery and its relationship with pseudocapacitors, and reviews selectively some recent progresses in the relevant research and development.

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Section: Cnt-poapmentioning

confidence: 99%

Redox electrode materials for supercapatteries

Chen

2016

Journal of Power Sources

207

111

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“…Residual ferrous nanoparticles remaining from the chemical vapor deposition synthesis process of carbon nanotubes are located within the caps of the MWNTs . To create an optimal material that is suitable for liquid‐solid interfacial Faradaic reactions, the nanoparticles must be accessible to charge transfer with the electrolyte and the MWNTs must maintain a relatively high conductivity by limiting the disruption to the π‐electron system.…”

Section: Resultsmentioning

confidence: 64%

“…In this article, we describe a method to oxidize MWNTs to expose the lingering catalysts from their synthesis (6–9 wt %), which creates redox‐active iron nanoparticles within the MWNTs. Previously, we performed electrochemical methods to activate these MWNTs, which proved efficacious in opening the end caps and improving electrochemical performance; however, a solution method has advantages in scalability and uniformity . MWNTs have been chemically oxidized using piranha solution, H 2 O 2 , KMnO 4 , HClO 4 , and O 3 to unzip their nanotube structures.…”

Section: Introductionmentioning

confidence: 98%

“…These dopants are inactive in CNT electrodes because they are blocked from the electrolyte by the graphitic layers of the MWNTs . However, our previous work demonstrated if these MWNTs are activated by exposing the electrode to high voltage, oxygen bubbles will nucleate on the metal nanoparticles and cause the MWNTs to ruptures near the end caps . This permits the electrochemical redox reactions of the metal nanoparticles to be harnessed revealing a specific capacitance of 290 F g −1 or a 61 % increase over their SWNT counterparts and exceeding the theoretical limits on MWNT supercapacitors.…”

Section: Introductionmentioning

confidence: 99%

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Creating Faradaic Carbon Nanotube Electrodes with Mild Chemical Oxidation

Emmett

Kowalske

Mou

et al. 2019

Batteries & Supercaps

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The development of new materials to improve interfacial charge transfer characteristics will drastically improve energy storage, heterogeneous catalysis, and many other electrochemical applications. Here, we report a simple procedure that can harness the Faradaic nature of residual iron nanoparticle catalysts that endure within multi-walled carbon nanotubes (MWNT) post-synthesis, thereby alleviating the challenges associated with forging hybrid nanocomposite electrodes. Nonpurified MWNTs, undergo a chemical oxidation process in acidic conditions with KMnO 4 to partially "unzip" the MWNTs and expose the redox-active iron nanoparticles to the electrolyte. A stable redox peak associated with the Fe 2 + /3 + transition is achieved during the MWNT oxidation process yielding a~350 % increase in capacitance (> 300 F g À 1 ) relative to purified MWNT electrodes (70 F g À 1 ). While these materials solely may be pragmatic as energy storage electrodes, the integration of redox species within an inert carbon electrode will also provide new opportunities to accelerate heterogeneous charge transfer reactions.

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“…The filter paper is then recycled. In preliminary experiments, we have prepared buckypapers using the recipe described above, which under voltammetric cycling in sulfuric acid showed a combination of EDLC and Faradaic energy storage arising from the defects and impurities present in the electrode [14]. The cross-sectional SEM images of an industrial-grade aluminum ribbon, which show micron-wide pores that span across its thickness.…”

Section: A B C Figure 4: (A)mentioning

confidence: 99%

Energy and our future: a perspective from the Clemson Nanomaterials Center

Rao

2015

Nanotechnology Reviews

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Our increasing energy demands have spurred a rigorous search for renewable energy sources to reduce our dependence on fossil fuels. However, efficient use of renewable energy is possible only with advances in both energy generation and storage. Today's batteries and capacitors, which are the main energy storage devices, cannot meet the world's demand for combined power and energy densities. To enhance the viability of such energy storing devices, the Clemson Nanomaterials Center (CNC) has developed a mix of scalable processes for carbon nanotube-based hybrid electrodes that show promise as a costeffective alternative to standard activated carbon-based electrodes. Working together with industrial partners, CNC has fabricated supercapacitors with energy and power densities in the range of ~11-35 Wh/kg and ~1.2-9 W/kg, respectively. Although this research development is transformative, further studies to optimize the separator and electrolyte technologies are needed to maximize both the energy and power density in a single device.

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Can Faradaic Processes in Residual Iron Catalyst Help Overcome Intrinsic EDLC Limits of Carbon Nanotubes?

Cited by 16 publications

References 24 publications

Redox electrode materials for supercapatteries

Redox electrode materials for supercapatteries

Creating Faradaic Carbon Nanotube Electrodes with Mild Chemical Oxidation

Energy and our future: a perspective from the Clemson Nanomaterials Center

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