THESIS
2021
1 online resource (xxxiii, 98 pages) : illustrations (some color)
Abstract
The fundamental understanding of active sites for various important electrochemical reactions
is studied theoretically and experimentally. We synthesized stone-wales (SW) defects rich
nitrogen-doped graphene (DG) with specific coordination of carbon atom rings. It reveals that
the SW rich defects rings (e.g.,5, 585, or 5775) appear correspondingly with carbon rings that
brought active sites during catalytic reactions. Moreover, we anchored dual isolated metallic
atoms (Ni/Fe) on DG support via linkers (O/N) to make its hybrids. DFT calculations are used
to study the mechanistic understanding of SW defects rich support with dual metal single
atoms. Numerous experimental tools such as XAS (XANES, EXAFS), STEM, XPS etc., are
used to study detailed experimental insights. The proposed struct...[
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The fundamental understanding of active sites for various important electrochemical reactions
is studied theoretically and experimentally. We synthesized stone-wales (SW) defects rich
nitrogen-doped graphene (DG) with specific coordination of carbon atom rings. It reveals that
the SW rich defects rings (e.g.,5, 585, or 5775) appear correspondingly with carbon rings that
brought active sites during catalytic reactions. Moreover, we anchored dual isolated metallic
atoms (Ni/Fe) on DG support via linkers (O/N) to make its hybrids. DFT calculations are used
to study the mechanistic understanding of SW defects rich support with dual metal single
atoms. Numerous experimental tools such as XAS (XANES, EXAFS), STEM, XPS etc., are
used to study detailed experimental insights. The proposed structure exhibits high catalytic
activity and stability towards OER and ORR for a longer duration in an alkaline medium, with
even better performance and stability than commercial Pt/C. We used laser irradiation
techniques to optimize the porous structure of nanocarbon and use it as a supportive matrix via
dangling bonding approach to extract metal atoms species from Co and Fe bulk metal foams
and demonstrated as SAC for HER-ORR catalysts. The isolated metal SA are confirmed via
AC-STEM, XANES and EXAFS. DFT simulations using the GCP-K model has been used to
understand the mechanism at varying applied potentials. Moreover, we also applied Mn
SA and
Mn
Cluster doped C
2N supported hybrids towards bifunctional (OER-HER) in alkaline media
towards stable catalytic performance for 24 hours without deflection. The experimental
evidence and theoretical mechanism are highlighted through characterizations, including ADF-STEM,
XANES/EXAFS and DFT calculations. Mn
Cluster on C
2N support requires a very low
overpotential of 57 mV and 282 mV, a current density of 10 mA cm
-2 towards HER and OER,
respectively. Our consistent experimental and theoretical findings inaugurate an avenue
towards designing rational catalysts intended for several important reactions like NRR and
CO
2RR.
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