Transition-metal-
and nitrogen-codoped carbide-derived carbon/carbon
nanotube composites (M-N-CDC/CNT) have been prepared, characterized,
and used as cathode catalysts in anion-exchange membrane fuel cells
(AEMFCs). As transition metals, cobalt, iron, and a combination of
both have been investigated. Metal and nitrogen are doped through
a simple high-temperature pyrolysis technique with 1,10-phenanthroline
as the N precursor. The physicochemical characterization shows the
success of metal and nitrogen doping as well as very similar morphologies
and textural properties of all three composite materials. The initial
assessment of the oxygen reduction reaction (ORR) activity, employing
the rotating ring–disk electrode method, indicates that the
M-N-CDC/CNT catalysts exhibit a very good electrocatalytic performance
in alkaline media. We find that the formation of HO
2
–
species in the ORR catalysts depends on the specific
metal composition (Co, Fe, or CoFe). All three materials show excellent
stability with a negligible decline in their performance after 10000
consecutive potential cycles. The very good performance of the M-N-CDC/CNT
catalyst materials is attributed to the presence of M-N
x
and pyridinic-N moieties as well as both micro-
and mesoporous structures. Finally, the catalysts exhibit excellent
performance in in situ tests in H
2
/O
2
AEMFCs,
with the CoFe-N-CDC/CNT reaching a current density close to 500 mA
cm
–2
at 0.75 V and a peak power density (
P
max
) exceeding 1 W cm
–2
. Additional
tests show that
P
max
reaches 0.8 W cm
–2
in an H
2
/CO
2
-free air system
and that the CoFe-N-CDC/CNT material exhibits good stability under
both AEMFC operating conditions.
Antibacterial drug-loaded electrospun nano- and microfibrous dressings are of major interest as novel topical drug delivery systems in wound care. In this study, chloramphenicol (CAM)-loaded polycaprolactone (PCL) and PCL/poly(ethylene oxide) (PEO) fiber mats were electrospun and characterized in terms of morphology, drug distribution, physicochemical properties, drug release, swelling, cytotoxicity, and antibacterial activity. Computational modeling together with physicochemical analysis helped to elucidate possible interactions between the drug and carrier polymers. Strong interactions between PCL and CAM together with hydrophobicity of the system resulted in much slower drug release compared to the hydrophilic ternary system of PCL/PEO/CAM. Cytotoxicity studies confirmed safety of the fiber mats to murine NIH 3T3 cells. Disc diffusion assay demonstrated that both fast and slow release fiber mats reached effective concentrations and had similar antibacterial activity. A biofilm formation assay revealed that both blank matrices are good substrates for the bacterial attachment and formation of biofilm. Importantly, prolonged release of CAM from drug-loaded fibers helps to avoid biofilm formation onto the dressing and hence avoids the treatment failure.
Non-precious-metal catalysts are
promising alternatives for Pt-based
cathode materials in low-temperature fuel cells, which is of great
environmental importance. Here, we have investigated the bifunctional
electrocatalytic activity toward the oxygen reduction reaction (ORR)
and the oxygen evolution reaction (OER) of mixed metal (FeNi; FeMn;
FeCo) phthalocyanine-modified multiwalled carbon nanotubes (MWCNTs)
prepared by a simple pyrolysis method. Among the bimetallic catalysts
containing nitrogen derived from corresponding metal phthalocyanines,
we report the excellent ORR activity of FeCoN-MWCNT and FeMnN-MWCNT
catalysts with the ORR onset potential of 0.93 V and FeNiN-MWCNT catalyst
for the OER having
E
OER
= 1.58 V at 10
mA cm
–2
. The surface morphology, structure, and
elemental composition of the prepared catalysts were examined with
scanning electron microscopy, X-ray diffraction, and X-ray photoelectron
spectroscopy. The FeCoN-MWCNT and FeMnN-MWCNT catalysts were prepared
as cathodes and tested in anion-exchange membrane fuel cells (AEMFCs).
Both catalysts displayed remarkable AEMFC performance with a peak
power density as high as 692 mW cm
–2
for FeCoN-MWCNT.
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