19 research outputs found
Alveoli-inspired facile transport structure of N-doped porous carbon for electrochemical energy applications
Heteroatom-doped porous carbon materials have attracted much attention
because of their extensive application in energy conversion and storage
devices. Because the performance of fuel cells and the rate capability of
supercapacitors depend signifi cantly on multiple factors, such as electrical
conductivity and transport rate of ions and reactants, designing these carbonbased
materials to optimize performance factors is vital. In order to address
these issues, alveoli that possess a hollow cavity where oxygen exchange
can occur are synthesized, inspired by N-doped carbon materials with a
high surface area and low transport resistance. By incorporating a dopamine
coating on zeolitic imidazolate framework (ZIF), pore size is modifi ed and
electrical conducting pathways are constructed, resulting in changes to the
reaction kinetics. These highly interconnected electron connection channels
and proper pore sizes facilitate the diffusion of reactants and the conduction
of electrons, leading to high activity of the oxygen reduction reaction (ORR),
which is comparable to Pt, and high rate performance in supercapacitors.142481sciescopu
Low-Temperature and Gram-Scale Synthesis of Two-Dimensional FeāNāC Carbon Sheets for Robust Electrochemical Oxygen Reduction Reaction
The
FeāNāC-based carbon materials, which are generally
formed by high-temperature annealing, have been highlighted as a promising
alternative to expensive Pt electrocatalysts for oxygen reduction
reaction. However, the delicate formation of active sites remains
an issue because of decomposition and transformation of the macrocycle
during heat treatment. Accordingly, we developed a low-temperature
and gram-scale approach to synthesizing iron phthalocyanine (Pc)-embedded
two-dimensional carbon sheets by annealing at 450 Ā°C. The low-temperature
annealing process, which is motivated by the synthesis of carbon nanoribbons,
is suitable for maintaining the FeāNāC structure while
enhancing coupling with carbon. Our two-dimensional carbon sheets
show higher ORR activity than commercial Pt catalyst in alkaline media.
Furthermore, the feasibility of real application to alkaline membrane
electrolyte fuel cell is verified by superior volumetric current density.
In durability point of view, the initial activity is retained up to
3000 potential cycles without appreciable activity loss; this excellent
performance is attributed to the structural stabilization and electron
donation from the carbon sheet, which occurs via strong electronic
coupling. We believe that this low-temperature and large-scale synthesis
of a carbon structure will provide new possibilities for the development
of electrochemical energy applications
Ordered macroporous platinum electrode and enhanced mass transfer in fuel cells using inverse opal structure
Three-dimensional, ordered macroporous materials such as inverse opal structures are attractive materials for various applications in electrochemical devices because of the benefits derived from their periodic structures: relatively large surface areas, large voidage, low tortuosity and interconnected macropores. However, a direct application of an inverse opal structure in membrane electrode assemblies has been considered impractical because of the limitations in fabrication routes including an unsuitable substrate. Here we report the demonstration of a single cell that maintains an inverse opal structure entirely within a membrane electrode assembly. Compared with the conventional catalyst slurry, an ink-based assembly, this modified assembly has a robust and integrated configuration of catalyst layers; therefore, the loss of catalyst particles can be minimized. Furthermore, the inverse-opal-structure electrode maintains an effective porosity, an enhanced performance, as well as an improved mass transfer and more effective water management, owing to its morphological advantages.180951sciescopu
Understanding Interface between Electrode and Electrolyte: Organic/Inorganic Hybrid Design for Fast Ion Conductivity
Ion transport is an important issue
in electrochemical-based energy conversion and storage devices. Ion
transport at the interface of the electrode and electrolyte is critical
for performance. However, there is little understanding of the interface
phenomena based on ion transport properties. Here, the proton transport
behavior in a Nafion membrane (electrolyte) and that of an ionomer
in the catalyst layer (electrode/electrolyte interface) was investigated
simultaneously by electrochemical impedance spectroscopy. Our study
indicates that the proton transport behavior in the catalyst layer
is different from that in membrane. To elucidate the interface phenomena,
we analyzed the Nafion electrolyte and proton behavior by molecular
dynamics (MD). On the basis of the MD results, we modified the catalyst
with a hybrid of inorganic Pt catalyst and organic 3-mercaptopropionic
acid to promote a positive interfacial reaction between the electrolyte
and electrode, which resulted in improved proton transport and performance
Anaplastic Lymphoma Kinase Translocation A Predictive Biomarker of Pemetrexed in Patients with Non-small Cell Lung Cancer
Introduction: This study compared the efficacy of pemetrexed in patients with anaplastic lymphoma kinase (ALK)-positive versus ALK-negative (epidermal growth factor receptor [EGFR] mutant or wild type [WT] for both ALK and EGFR) non-small cell lung cancer (NSCLC). Methods: Patients with advanced NSCLC who received second-line pemetrexed and beyond between March 2007 and April 2010 were screened for EGFR mutations and ALK rearrangements at Seoul National University Hospital. The clinical and in vitro efficacy of pemetrexed was evaluated for each genotypic group. Results: Ninety-five NSCLC patients were genotyped as follows: 43 (45%) EGFR mutation, 15 (16%) ALK translocation, and 37 (39%) WT. The overall response rate was superior in ALK-translocated patients compared with EGFR mutant or WT patients (46.7 versus 4.7 versus 16.2%, p = 0.001). ALK-positive patients showed longer time to progression than EGFR mutant or WT patients (9.2 versus 1.4 versus 2.9 months, p = 0.001). ALK positivity alone was a significant predictor for overall response rate (hazard ratio [HR] = 0.07, 95% confidence interval [CI]: 0.01-0.32; p = 0.001) and time to progression (HR = 0.44, 95% CI: 0.24-0.80; p = 0.007). ALK positivity remained independently significant regardless of treatment line (HR = 0.43, 95% CI: 0.24-0.77; p = 0.005). Thymidylate synthase mRNA levels in ALK-positive cells were significantly lower compared with control cells (p < 0.05). Conclusion: Pemetrexed is an effective treatment in patients with ALK-positive NSCLC. ALK positivity was independently predictive of pemetrexed efficacy in NSCLC patients.