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Microwave enabled fabrication of highly conductive graphene and porous carbon/metal hybrids for sustainable catalysis and energy storage

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Title
Microwave enabled fabrication of highly conductive graphene and porous carbon/metal hybrids for sustainable catalysis and energy storage
Name (type = personal)
NamePart (type = family)
Savaram
NamePart (type = given)
Keerthi
NamePart (type = date)
1989-
DisplayForm
Keerthi Savaram
Role
RoleTerm (authority = RULIB)
author
Name (type = personal)
NamePart (type = family)
He
NamePart (type = given)
Huixin
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Huixin He
Affiliation
Advisory Committee
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chair
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NamePart (type = family)
Lockard
NamePart (type = given)
Jenny
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Jenny Lockard
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Advisory Committee
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internal member
Name (type = personal)
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Huskey
NamePart (type = given)
Phillip
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Phillip Huskey
Affiliation
Advisory Committee
Role
RoleTerm (authority = RULIB)
internal member
Name (type = personal)
NamePart (type = family)
Wang
NamePart (type = given)
Chunsheng
DisplayForm
Chunsheng Wang
Affiliation
Advisory Committee
Role
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outside member
Name (type = corporate)
NamePart
Rutgers University
Role
RoleTerm (authority = RULIB)
degree grantor
Name (type = corporate)
NamePart
Graduate School - Newark
Role
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school
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Text
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theses
OriginInfo
DateCreated (qualifier = exact)
2017
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2017-10
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2017
Place
PlaceTerm (type = code)
xx
Language
LanguageTerm (authority = ISO639-2b); (type = code)
eng
Abstract (type = abstract)
Carbon is the most abundant material next to oxygen in terms of sustainability. The potential of carbon based materials has been recognized in recent decades by the discovery of fullerene (1996 Nobel prize in chemistry), carbon nanotubes (2008 Kavli prize in nanoscience) and graphene (2010 Nobel prize in physics). The synthesis of carbon materials with well controlled morphologies lead to their exploration in both fundamental research and industrial applications. Graphene also commonly referred to as a wonder material has been under extensive research for more than a decade, due to its excellent electronic, optical, thermal and mechanical properties. However, the realization of these applications for practical purposes require its large scale synthesis. The common method of graphene synthesis involves reduction of graphene oxide. Nevertheless, complete restoration of intact graphene basal plane destroyed by oxidation cannot be achieved, limiting the application of as synthesized graphene in flexible macro electronics, mechanically and electronically reinforced composites etc. Hence, research was pursued in regards to achieve controlled oxidation, sufficient enough to overcome the Vander-Waals forces and preserving the graphene domains. One such approach reported by our group is the solution processable graphene achieved via controlled oxidation, by the use of nitronium oxidation approach. However, toxic NOx gases and byproducts generated during the synthesis, limits the scalability of this approach. In this thesis, for the first time, we reported the synergy of piranha etching solution with intercalated graphite for the controlled oxidation of graphite particles via microwave heating in chapter 2. The controlled oxidation leads to rapid (60 seconds) and direct generation of highly conductive, clean low oxygen containing graphene sheets without releasing any detectable toxic gases or aromatic by-products as demonstrated by gas chromatography-mass spectrometry. These highly conductive graphene sheets have unique molecular structures, different from both graphene oxide and pristine graphene sheets. They can be dispersed in both aqueous and common organic solvents without surfactants/stabilizers producing “clean” graphene sheets in solution phase. “Paper-like” graphene films are generated via simple filtration resulting in films with a conductivity of 2.26 × 104 S m-1, the highest conductivity observed for graphene films assembled via vacuum filtration from solution processable graphene sheets to date. After 2-hour low temperature annealing at 300 C, the conductivity further increased to 7.44 × 104 S m-1. This eco-friendly and rapid approach for scalable production of highly conductive and “clean” solution-phase graphene sheets would enable a broad spectrum of applications at low cost. Irrespective of the vast applications of highly conductive graphene, it exhibits limited catalytic centers, is impervious, and limits the diffusion of ions. This inadequacy can be overcome by the hole generation on highly conductive graphene. Current approaches for large scale production of holey graphene require graphene oxide (GO) or reduced GO (rGO) as starting materials. Thus generated holey graphene derivatives still contain a large number of defects on their basal planes, which not only complicates fundamental studies, but also influences certain practical applications due to their largely decreased conductivity, thermal and chemical stability. This work reports a novel scalable approach exploiting the wireless joule heating mechanism provided by microwave irradiation of partially oxidized graphite intercalation compounds in chapter 3. The wireless joule heating mechanism affords region-selective heating, which not only enable fabrication of holey graphene materials with their basal plane nearly intact, but also engineers the edges associated with holes to be rich in zigzag geometry. The term pristine holey graphene was given, to differentiate from the holey graphene derivatives with basal plane defects, as reported in the literature. The pristine holey graphene with zigzag edges were studied and explored as a metal free catalyst for reduction reactions via hydrogen atom transfer mechanism. The pristine holey graphene nanoplatelets not only exhibited high catalytic activity and desired selectivity, but also provided excellent chemical stability for recyclability, which is very different from its counterpart holey graphene derivatives with basal plane defects. It was also reported that the reduction of nitrobenzene occurs via condensation pathway with this catalyst. To further provide insight into combustion of graphite in air with microwave irradiation, the stabilized intercalated graphene without point defects was used to generate holes in chapter 4. The co-intercalated O2 into graphite intercalated compound act as the internal oxidant, to oxidize the carbon, along with the surrounding air. High local temperatures were achieved via joule heating mechanism, hence promoting combustion of graphene to generate holes and edges. We observed that in combination to hole generation, higher conductivity was also observed in comparison to the holey graphene synthesized in chapter 3. The highly conductive holey graphene was tested for their electro-catalytic activity in the reduction of oxygen. The reduction of oxygen occurs via 2e- pathway, where peroxide with 90% yield was recorded. This opens path for onsite peroxide production in alkaline media, and therefore allowing its use in bleaching industries. In concern of carbon based materials being explored for catalysis, their high amount to facilitate the reaction, limits practicality of the catalyst for industrial applications. However, the immobilization of metal nanoparticles onto porous carbon supports, synthesized from sustainable and cheap biomass was widely pursued. It was widely reported that the doping of carbon support with N further improved their interaction with the metal and promoted higher catalytic activity. In chapter 5, for the first time, the influence of P doped carbon support on catalytic activity of Pd was reported. A single step microwave assisted fabrication of Pd embedded into porous phosphorous doped graphene like carbon was demonstrated. Structural characterization revealed that, the metal nanoparticles are in the range of 10nm with a surface area of 1133m2/g. The developed method is not only sustainable as it is synthesized from biomass and anti-nutrient molecule (phytic acid), but also energy efficient as microwave irradiation (50sec) is used for the catalyst synthesis. The as synthesized catalyst recorded 90% conversion with a TOF of 23000h-1 for benzyl alcohol oxidation, which remained constant even after 8 recycles indicating the stability of catalyst. Different wt% of Pd onto PGC was tested for their alcohol oxidation capacity and found that the 3% Pd-PGc which activates O2 more towards 4e- in ORR has the best conversion and selectivity. The biomass molecule phytic acid used for the synthesis of phosphorous doped carbon support was also used as a phosphorous source in the synthesis of tin phosphides in chapter 6. Current studies have shown that sodium, a low cost and naturally abundant metal, can act as a substituent for lithium in lithium ion batteries (LIB), hence, allowing their applications in real world. This transition towards the use of sodium ion batteries (SIB) has entailed research to improve the cycle stability and energy density of battery by introducing tin phosphides as anodes for batteries. Tin phosphides exhibit a self-healing mechanism, hence decreases the capacity decay as observed in the case of Sn metal. However, it was reported that the self-healing mechanism is not completely reversible with partial pulverization observed. Therefore, we pursued a time efficient method to synthesize tin phosphide in a phosphorous doped carbon matrix (SnP@PGc) via microwave irradiation. The SnP@PGc formed when tested as anode for SIBs, demonstrated superior capacity of 515 mAh/g after 750 cycles at a charge and discharge current of 0.2 C. The superior cycle stability can be attributed to the protection against volume expansion by phosphorous doped porous carbon shell during battery charge and discharge process and hence mitigating the pulverization of tin phosphides.
Subject (authority = RUETD)
Topic
Chemistry
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Rutgers University Electronic Theses and Dissertations
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ETD_8344
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electronic resource
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text/xml
Extent
1 online resource (xxii, 210 p. : ill.)
Note (type = degree)
Ph.D.
Note (type = bibliography)
Includes bibliographical references
Subject (authority = ETD-LCSH)
Topic
Graphene
Note (type = statement of responsibility)
by Keerthi Savaram
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Title
Graduate School - Newark Electronic Theses and Dissertations
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rucore10002600001
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Identifier (type = doi)
doi:10.7282/T3319ZZX
Genre (authority = ExL-Esploro)
ETD doctoral
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The author owns the copyright to this work.
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Name
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Savaram
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Keerthi
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2017-09-12 15:13:13
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Keerthi Savaram
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Rutgers University. Graduate School - Newark
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I hereby grant to the Rutgers University Libraries and to my school the non-exclusive right to archive, reproduce and distribute my thesis or dissertation, in whole or in part, and/or my abstract, in whole or in part, in and from an electronic format, subject to the release date subsequently stipulated in this submittal form and approved by my school. I represent and stipulate that the thesis or dissertation and its abstract are my original work, that they do not infringe or violate any rights of others, and that I make these grants as the sole owner of the rights to my thesis or dissertation and its abstract. I represent that I have obtained written permissions, when necessary, from the owner(s) of each third party copyrighted matter to be included in my thesis or dissertation and will supply copies of such upon request by my school. I acknowledge that RU ETD and my school will not distribute my thesis or dissertation or its abstract if, in their reasonable judgment, they believe all such rights have not been secured. I acknowledge that I retain ownership rights to the copyright of my work. I also retain the right to use all or part of this thesis or dissertation in future works, such as articles or books.
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2017-10-31
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2019-10-31
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Access to this PDF has been restricted at the author's request. It will be publicly available after October 31st, 2019.
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