3 research outputs found
Zeolitic Imidazolate Framework-Derived Pt–Co in Nanofibrous Networks as Stable Oxygen Reduction Electrocatalysts with Low Pt Loading
Proton-exchange membrane fuel cell technology is a key
component
in the future zero-carbon energy system, generating power from carbon-free
fuels, such as green hydrogen. However, the high Pt loading in conventional
fuel cell electrodes to maintain electrocatalytic activity and durability,
especially on the cathode for oxygen reduction, is the Achilles heel
for the worldwide deployment of fuel cell technologies. To minimize
Pt consumption for oxygen reduction, we synthesized Pt–Co-based
electrocatalysts with meticulous structuring from micrometer to the
atomic scale based on reaction pathways. The resulting Pt–Co-based
electrocatalysts contain only 1.9 wt% Pt, which is 20 times lower
than the conventional Pt–C catalysts for fuel cells. By utilizing
electrospinning and in situ synthesis, we anchored three-dimensionally
structured zeolitic imidazolate frameworks on continuously connected
nanofibrous electrospun mats. The Pt–Co@Pt-free nanowire (PC@PFN)
electrocatalysts contain Pt–Co nanoparticles (NPs) and non-Pt
elements, Co-containing sites comprising NPs, nanoclusters, and N-coordinated
Co single atoms. Despite the ultralow Pt loading in PC@PFN, the mass
activity exceeds the U.S. Department of Energy 2025 target by 2.8
times and retains 85.5% of the initial activity after 80,000 durability
test cycles, possibly owing to synergistic reaction pathways between
Pt and non-Pt sites
Biofunctionalized Ceramic with Self-Assembled Networks of Nanochannels
Nature designs circulatory systems with hierarchically organized networks of gradually tapered channels ranging from micrometer to nanometer in diameter. In most hard tissues in biological systems, fluid, gases, nutrients and wastes are constantly exchanged through such networks. Here, we developed a biologically inspired, hierarchically organized structure in ceramic to achieve effective permeation with minimum void region, using fabrication methods that create a long-range, highly interconnected nanochannel system in a ceramic biomaterial. This design of a synthetic model-material was implemented through a novel pressurized sintering process formulated to induce a gradual tapering in channel diameter based on pressure-dependent polymer agglomeration. The resulting system allows long-range, efficient transport of fluid and nutrients into sites and interfaces that conventional fluid conduction cannot reach without external force. We demonstrate the ability of mammalian bone-forming cells placed at the distal transport termination of the nanochannel system to proliferate in a manner dependent solely upon the supply of media by the self-powering nanochannels. This approach mimics the significant contribution that nanochannel transport plays in maintaining living hard tissues by providing nutrient supply that facilitates cell growth and differentiation, and thereby makes the ceramic composite “alive”
High-Density Single-Layer Coating of Gold Nanoparticles onto Multiple Substrates by Using an Intrinsically Disordered Protein of α‑Synuclein for Nanoapplications
Functional
graffiti of nanoparticles onto target surface is an
important issue in the development of nanodevices. A general strategy
has been introduced here to decorate chemically diverse substrates
with gold nanoparticles (AuNPs) in the form of a close-packed single
layer by using an omni-adhesive protein of α-synuclein (αS)
as conjugated with the particles. Since the adsorption was highly
sensitive to pH, the amino acid sequence of αS exposed from
the conjugates and its conformationally disordered state capable of
exhibiting structural plasticity are considered to be responsible
for the single-layer coating over diverse surfaces. Merited by the
simple solution-based adsorption procedure, the particles have been
imprinted to various geometric shapes in 2-D and physically inaccessible
surfaces of 3-D objects. The αS-encapsulated AuNPs to form a
high-density single-layer coat has been employed in the development
of nonvolatile memory, fule-cell, solar-cell, and cell-culture platform,
where the outlying αS has played versatile roles such as a dielectric
layer for charge retention, a sacrificial layer to expose AuNPs for
chemical catalysis, a reaction center for silicification, and biointerface
for cell attachment, respectively. Multiple utilizations of the αS-based
hybrid NPs, therefore, could offer great versatility to fabricate
a variety of NP-integrated advanced materials which would serve as
an indispensable component for widespread applications of high-performance
nanodevices