Ruthenium (Ru) is the most widely used metal as an electrocatalyst for nitrogen (N2) reduction reaction (NRR) because of the relatively high N2 adsorption strength for successive reaction. Recently, it has been well reported that the homogeneous Ru‐based metal alloys such as RuRh, RuPt, and RuCo significantly enhance the selectivity and formation rate of ammonia (NH3). However, the metal combinations for NRR have been limited to several miscible combinations of metals with Ru, although various immiscible combinations have immense potential to show high NRR performance. In this study, an immiscible combination of Ru and copper (Cu) is first utilized, and homogeneous alloy nanoparticles (RuCu NPs) are fabricated by the carbothermal shock method. The RuCu homogeneous NP alloys on cellulose/carbon nanotube sponge exhibit the highest selectivity and NH3 formation rate of ≈31% and −73 μmol h−1 cm−2, respectively. These are the highest values of the selectivity and NH3 formation rates among existing Ru‐based alloy metal combinations.
For practical application of lithium–sulfur batteries (LSBs), it is crucial to develop sulfur cathodes with high areal capacity and cycle stability in a simple and inexpensive manner. In this study, a carbon cloth infiltrated with a sulfur-containing electrolyte solution (CC-S) was utilized as an additive-free, flexible, high-sulfur-loading cathode. A freestanding carbon cloth performed double duty as a current collector and a sulfur-supporting/trapping material. The active material in the form of Li2S6 dissolved in a 1 M LiTFSI-DOL/DME solution was simply infiltrated into the carbon cloth (CC) during cell fabrication, and its optimal loading amount was found to be in a range between 2 and 10 mg/cm2 via electrochemical characterization. It was found that the interwoven carbon microfibers retained structural integrity against volume expansion/contraction and that the embedded uniform micropores enabled a high loading and an efficient trapping of sulfur species during cycling. The LSB coin cell employing the CC-S electrode with an areal sulfur loading of 6 mg/cm2 exhibited a high areal capacity of 4.3 and 3.2 mAh/cm2 at C/10 for 145 cycles and C/3 for 200 cycles, respectively, with minor capacity loss (<0.03%/cycle). More importantly, such high performance could also be realized in flexible pouch cells with dimensions of 2 cm × 6 cm before and after 300 bending cycles. Simple and inexpensive preparation of sulfur cathodes using CC-S electrodes, therefore, has great potential for the manufacture of high-performance flexible LSBs.
Mineralized collagen
fibrils are important basic building blocks
of calcified tissues, such as bone and dentin. Polydopamine (PDA)
can introduce functional groups, i.e., hydroxyl and amine groups,
on the surfaces of type I collagen (Col-I) as possible nucleation
sites of calcium phosphate (CaP) crystallization. Molecular bindings
in between PDA and Col-I fibrils (Col-PDA) have been found to significantly
reduce the interfacial energy. The wetting effect, mainly hydrophilicity
due to the functional groups, escalates the degree of mineralization.
The assembly of Col-I molecules into fibrils was initiated at the
designated number of collagenous molecules and PDA. In contrast to
the infiltration of amorphous calcium phosphate (ACP) precursors into
the Col-I matrix by polyaspartic acid (pAsp), this collagen assembly
process allows nucleation and ACP to exist in advance by PDA in the
intrafibrillar matrix. PDA bound to specific sites, i.e., gap and
overlap zones, by the regular arrangement of Col-I fibrils enhanced
ACP nucleation and thus mineralization. As a result, the c-axis-oriented platelets of crystalline hydroxyapatite in the Col-I
fibril matrix were observed in the enhanced mineralization through
PDA functionalization.
We report that controlled graphitic carbon nitride (g-CN) which has high aspect ratio and expanded interlayer spacing can exhibit lyotropic liquid crystalline (LC) phase in concentrated sulfuric acid. By utilizing its LC phase, a g-CN fiber for the first time was successfully fabricated.
Highly selective electrocatalytic CO2 reduction
for
CO production has attracted tremendous attention for achieving the
forthcoming goals of carbon neutrality and widespread industrial utilization
and recycling of carbon. Among various approaches, the structural
control of the catalyst is particularly interesting because of the
facile control of CO2 reduction conditions, such as reaction
media and reaction pathways. Thus far, a wide range of nanostructured
catalysts, including Au needle tips, Au nanowires, and Au wrinkles,
have been used for the enhancement of the selectivity of CO production.
In this study, an electrocatalyst with a hierarchical nanostructure
for the highly selective production of CO is reported. This hierarchical
structure is fabricated by the deposition of Au via e-beam evaporation
on a dendritic fibrous nanosilica (KCC-1) template, which is a spherical
silica particle consisting of uniformly distributed center-radial
fibers. The conversion efficiency of this catalyst is strongly affected
by the thickness of the Au deposited on the KCC-1 template, and the
highest CO selectivity of ∼98% (at −0.5 V vs. RHE) is
obtained at an optimum Au thickness of 50 nm. According to the CO2 electrocatalytic reduction results obtained from KCC-1 with
dendritic fibers and a conventional spherical particle without the
fibers under various electrolyte conditions, such selectivity enhancement
of Au on the KCC-1 template is attributed to the increase in the local
pH near the hierarchical catalyst surface. This work provides potential
promising templates that exhibit a unique nanostructure for efficient
electrocatalysis.
Highly loaded Au nanoseeds (∼ 65 wt%) without aggregation by introducing highly defective substrate and carbothermalshock method showed high stability inhibiting Li dendrite growh in Li-metal batteries.
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