5 research outputs found
Palladium Intercalated into the Walls of Mesoporous Silica as Robust and Regenerable Catalysts for Hydrodeoxygenation of Phenolic Compounds
Nanostructured noble-metal catalysts
traditionally suffer from
sintering under high operating temperatures, leading to durability
issues and process limitations. The encapsulation of nanostructured
catalysts to prevent loss of activity through thermal sintering, while
maintaining accessibility of active sites, remains a great challenge
in the catalysis community. Here, we report a robust and regenerable
palladium-based catalyst, wherein palladium particles are intercalated
into the three-dimensional framework of SBA-15-type mesoporous silica.
The encapsulated Pd active sites remain catalytically active as demonstrated
in high-temperature/pressure phenol hydrodeoxygenation reactions.
The confinement of Pd particles in the walls of SBA-15 prevents particle
sintering at high temperatures. Moreover, a partially deactivated
catalyst containing intercalated particles is regenerated almost completely
even after several reaction cycles. In contrast, Pd particles, which
are not encapsulated within the SBA-15 framework, sinter and do not
recover prior activity after a regeneration procedure
Mechanistic Study of Shape-Anisotropic Nanomaterials Synthesized via Spontaneous Galvanic Displacement
Among the broad portfolio
of preparations for nanoscale materials,
spontaneous galvanic displacement (SGD) is emerging as an important
technology because it is capable of creating functional nanomaterials
that cannot be obtained through other routes and may be used to thrift
precious metals used in a broad range of applications including catalysis.
With advances resulting from increased understanding of the SGD process,
materials that significantly improve efficiency and potentially enable
widespread adoption of next generation technologies can be synthesized.
In this work, PtAg nanotubes synthesized via displacement of Ag nanowires
by Pt were used as a model system to elucidate the fundamental mechanisms
of SGD. Characterization by X-ray diffraction (XRD), small-angle X-ray
scattering (SAXS), and atom probe tomography (APT) indicates nanotubes
are formed as Ag is oxidized first from the surface and then from
the center of the nanowire, with Pt deposition forming a rough, heterogeneous
surface on the PtAg nanotube
Mechanistic Study of Shape-Anisotropic Nanomaterials Synthesized via Spontaneous Galvanic Displacement
Among the broad portfolio
of preparations for nanoscale materials,
spontaneous galvanic displacement (SGD) is emerging as an important
technology because it is capable of creating functional nanomaterials
that cannot be obtained through other routes and may be used to thrift
precious metals used in a broad range of applications including catalysis.
With advances resulting from increased understanding of the SGD process,
materials that significantly improve efficiency and potentially enable
widespread adoption of next generation technologies can be synthesized.
In this work, PtAg nanotubes synthesized via displacement of Ag nanowires
by Pt were used as a model system to elucidate the fundamental mechanisms
of SGD. Characterization by X-ray diffraction (XRD), small-angle X-ray
scattering (SAXS), and atom probe tomography (APT) indicates nanotubes
are formed as Ag is oxidized first from the surface and then from
the center of the nanowire, with Pt deposition forming a rough, heterogeneous
surface on the PtAg nanotube
Mechanistic Study of Shape-Anisotropic Nanomaterials Synthesized via Spontaneous Galvanic Displacement
Among the broad portfolio
of preparations for nanoscale materials,
spontaneous galvanic displacement (SGD) is emerging as an important
technology because it is capable of creating functional nanomaterials
that cannot be obtained through other routes and may be used to thrift
precious metals used in a broad range of applications including catalysis.
With advances resulting from increased understanding of the SGD process,
materials that significantly improve efficiency and potentially enable
widespread adoption of next generation technologies can be synthesized.
In this work, PtAg nanotubes synthesized via displacement of Ag nanowires
by Pt were used as a model system to elucidate the fundamental mechanisms
of SGD. Characterization by X-ray diffraction (XRD), small-angle X-ray
scattering (SAXS), and atom probe tomography (APT) indicates nanotubes
are formed as Ag is oxidized first from the surface and then from
the center of the nanowire, with Pt deposition forming a rough, heterogeneous
surface on the PtAg nanotube
Iron Pyrite Nanocrystal Inks: Solvothermal Synthesis, Digestive Ripening, and Reaction Mechanism
Colloidal
iron pyrite nanocrystals (or FeS<sub>2</sub> NC inks)
are desirable as active materials in lithium ion batteries and photovoltaics
and are particularly suitable for large-scale, roll-to-roll deposition
or inkjet printing. However, to date, FeS<sub>2</sub> NC inks have
only been synthesized using the hot-injection technique, which requires
air-free conditions and may not be desirable at an industrial scale.
Here, we report the synthesis of monodisperse, colloidal, spherical,
and phase-pure FeS<sub>2</sub> NCs of 5.5 ± 0.3 nm in diameter
via a scalable solvothermal method using iron diethyldithiocarbamate
as the precursor, combined with a postdigestive ripening process.
The phase purity and crystallinity are determined using X-ray diffraction,
transmission electron microscopy, far-infrared spectroscopy, and Raman
spectroscopy techniques. Through this study, a hypothesis has been
verified that solvothermal syntheses can also produce FeS<sub>2</sub> NC inks by incorporating three experimental conditions: high solubility
of the precursor, efficient mass transport, and sufficient stabilizing
ligands. The addition of ligands and stirring decrease the NC size
and led to a narrow size distribution. Moreover, using density functional
theory calculations, we have identified an acid-mediated decomposition
of the precursor as the initial and critical step in the synthesis
of FeS<sub>2</sub> from iron diethyldithiocarbamate