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Cell reversal is observed when a current load is applied to the polymer electrolyte membrane fuel cell under fuel starvation conditions. Cell reversal causes severe corrosion (or oxidation) of the carbon support in the anode, which leads to a decrease in overall fuel cell performance. To suppress the corrosion reaction of carbon under cell reversal conditions and to increase the durability of fuel cells, studies on anode additives are being conducted. However, studies on the effect of additives on catalysts with different platinum contents have not been conducted. In this study, 20 wt%, 40 wt%, 60 wt% commercial Pt/C catalyst was applied to the anode, and 50 cycles of cell reversal were performed. Furthermore, the performance change with and without IrO2 as an additive was observed and its effect was assessed. Changes in the morphologies of the electrodes before and after cell reversal tests were also observed using a transmission electron microscope and a scanning electron microscope. The higher the platinum content of the catalyst, the more resistant to cell reversal. In addition, the addition of IrO2 to the anode effectively prevents performance degradation due to cell reversal.

An ideal polymer electrolyte membrane fuel cell (PEMFC) is one that continuously generates electricity as long as hydrogen and oxygen (or air) are supplied to its anode and cathode, respectively. However, internal and/or external conditions could bring about the degradation of its electrodes, which are composed of nanoparticle catalysts. Particularly, when the hydrogen supply to the anode is disrupted, a reverse voltage is generated. This phenomenon, which seriously degrades the anode catalyst, is referred to as cell reversal. To prevent its occurrence, iridium oxide (IrO2) particles were added to the anode in the membrane-electrode assembly of the PEMFC single-cells. After 100 cell reversal cycles, the single-cell voltage profiles of the anode with Pt/C only and the anodes with Pt/C and various IrO2 contents were obtained. Additionally, the cell reversal-induced degradation phenomenon was also confirmed electrochemically and physically, and the use of anodes with various IrO2 contents was also discussed.

A variety of methods have been developed for accurate and systematic evaluation of chemical genotoxicity. Ceric ammonium nitrate (CAN) and 1,3-propane sultone (1,3-PS) have been extensively applied in industrial fields. Although 1,3-PS, but not CAN, has been reported as a potent carcinogen, systematic assessment of the genotoxic properties of these chemicals has not been conducted. The purpose of this study was to establish a decision tree for evaluating genotoxicity based on the good laboratory practices (GLP) system using 1,3-PS and CAN as test chemicals. In vitro studies were performed including the bacterial reverse mutation assay, chromosomal aberration assay, and micronucleus assay. We conducted in vivo studies using a combined micronucleus and alkaline comet (MN-CMT) assay and the Pig-a gene mutation assay, which is a promising method for detecting gene mutations in vivo. CAN showed negative responses in all in vitro genotoxicity assays and the in vivo combined MN-CMT assay. Meanwhile, 1,3-PS had positive results in all in vitro and in vivo genotoxicity assays. In this study, we confirmed the genotoxicity of 1,3-PS and CAN using both in vitro and in vivo assays. We propose a decision tree for evaluating chemical-induced genotoxicity.

Background Clinically, liver fibrosis and cholestasis are two major disease entities, ultimately leading to hepatic failure. Although autophagy plays a substantial role in the pathogenesis of these diseases, its precise mechanism has not been determined yet. Materials and methods Mouse models of liver fibrosis or cholestasis were obtained after the serial administration of thioacetamide (TAA) or surgical bile duct ligation (BDL), respectively. Then, after obtaining liver specimens at specific time points, we compared the expression of makers related to apoptosis (cleaved caspases), inflammation (CD68), necrosis (high-mobility group box 1), phospho-c-Jun N-terminal kinase (p-JNK), and autophagy (microtubule-associated protein light chain 3B and p62) in the fibrotic or cholestatic mouse livers, by polymerase chain reaction, Western blot analysis, immunohistochemistry, and immunofluorescence. Results Although cholestatic livers exhibited the tendency of progressively increasing the expression of most apoptosis-related markers (cleaved caspases), it was not prominent when it was compared with the tendency found in the livers of TAA-treated mice. Contrastingly, the necrosis-related factor (high-mobility group box 1) was significantly increased in the livers of BDL mice over time, reaching their peak values on day 7 after BDL. In addition, the inflammation-related factor (CD68) was highly expressed in BDL mice compared with TAA-treated mice over time. Autophagy marker studies indicated that autophagy was upregulated in fibrotic livers, whereas it was downregulated in cholestatic livers. We also observed mild to moderate activation of p-JNK in the livers of TAA-treated mice, whereas significantly higher p-JNK activation was detected in the livers of BDL mice. Conclusions Unlike TAA-treated mice, BDL mice exhibited higher expression of the markers related with inflammation and necrosis, especially including p-JNK, while maintaining low levels of autophagic process. Therefore, obstructive cholestasis is characterized by higher p-JNK activation, which could be related with marked necrotic cell death resulting from extensive inflammation and little chance of compensatory autophagy.

Formic acid is a chemical with a simple molecular structure containing hydrogen. This liquid at room temperature is easy to handle and has a low toxicity, and is thus in the spotlight as a fuel. In particular, formic acid is an excellent fuel candidate because it can be operated at low temperatures when applied as a fuel in fuel cells with a high theoretical open-circuit voltage (1.48 V). However, it has a drawback in that the electrode catalyst is deactivated due to the generation of CO intermediates when formic acid is oxidized during cell operation. Therefore, to prevent this, an irreversibly adsorbed Bi on Pt catalyst is applied to a direct formic acid fuel cell (DFAFC) anode because it is easy to synthesize and economical. Physical analyses such as transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) were conducted, and electrochemical evaluations were performed through half-cell and single-cell level tests. The results revealed that the formic acid oxidation reaction activity of the Bi-modified Pt/C was 13 times higher than that of the conventional catalyst at 0.58 V. Further, a DFAFC stack was fabricated using the Bi-modified Pt/C, which yielded a power of 300 W. These results suggest that a simple synthesis method can be applied to fabricating industrially available DFAFC stacks.

Enhanced mass transport in polymer electrolyte membrane fuel cells (PEMFCs) is required for achieving high performance because concentration losses dominate cell performance. In particular, the flow field is crucial for mass transport. Recently, metal foam has been proposed as an alternative flow field owing to its three-dimensional pores, high porosity, and enhanced electrical conductivity. Here, we inspect the microstructure of various copper foams and investigate its effect as a flow field on PEMFCs. The PEMFCs with the optimized foam flow field deliver the highest performance reported to date. A large contact area and small ribs of the optimized foam flow field are advantageous for mass transfer and ohmic resistance. In addition, the internally generated pressure increases the partial pressure of the reactant, which leads to increased performance. This foam flow field has a significant potential for achieving high cell performance by enhancing the electrochemical reaction of the catalyst.

In this study, an iridium oxide (IrO2) inverse-opal membrane-electrode assembly (inverse-opal MEA) was fabricated via the decal-transfer method for an anode in polymer-electrolyte membrane water electrolysis (PEMWE) to decrease the loading of the noble catalyst. Electrodeposition parameters including current and total number of cycles were investigated to achieve the IrO2 inverse-opal electrode. The inverse-opal MEA with ultra-low loading exhibited outstanding performance that exceeded or was comparable to that obtained in other PEMWE studies. Additionally, it exhibited higher performance and lower ohmic and charge-transfer resistance when compared with that of commercial IrO2. Furthermore, the performance corresponded to the highest mass activity reported to date since the loading in the inverse-opal MEA was ultra-low. This was because the inverse-opal structure improved electron transfer owing to the interconnected pores and increased the surface area due to high porosity, thereby leading to the enhanced utilization of the catalyst.

An ideal oxygen reduction catalyst for use in fuel cells should exhibit both long-term durability and high activity. In this study, to increase the durability of highly loaded platinum- and platinum-nickel alloy catalysts possessing different types of carbon supports, a nitrogen-doped carbon shell was introduced on the catalyst surface through dopamine coating. As the catalyst surfaces were altered following shell formation, the ionomer contents of the catalyst inks were adjusted to optimise the three-phase boundary formation. Single cell tests were then conducted on these inks by applying them in a membrane electrolyte assembly. Furthermore, to confirm the durability of the catalysts under accelerated conditions, the operation was continued for 200 h at 70 °C and at a relative humidity of 100%. Transmission electron microscopy and electrochemical analysis were conducted before and after the durability tests, and the observed phenomena were discussed for catalysts bearing different types of carbon supports.

In this study, by treating not only the membrane but also the whole membrane electrode assembly (MEA) with KOH solution prior to incorporation in alkaline anion exchange membrane fuel cells, an ionic pathway for hydroxide conduction has optimized in the catalyst layer. This lowers the ohmic resistance of the KOH-treated MEA as detected by the polarization curve and impedance spectroscopy analysis. The process has greater advantage for non-platinum group metal (PGM) catalysts than PGM catalysts, because of the lower active site density and consequent high loading required for non-PGM catalysts.

We synthesized ordered mesoporous Fe/N/C with highly active Fe-N x /C sites denoted as m-FePhen-C as a non-precious metal catalyst (NPMC) for the oxygen reduction reaction in fuel cells. This was the first study that incorporated a catalyst precursor with Fe-N coordination directly in a simple block co-polymer-assisted soft-template method for the synthesis of mesoporous Fe/N/C. The synthesized catalyst (m-FePhen-C) showed a high catalytic performance comparable to that of Pt/C in half-cell tests, and a membrane electrode assembly (MEA) with an m-FePhen-C cathode exhibited 40% higher power density than did an MEA with a commercial Pt/C cathode in single-cell tests, with comparable electrode thicknesses. This result is highly meaningful in that generation of the Fe-N x /C active sites and formation of ordered mesoporous structure were achieved simultaneously in the simple soft-template-assisted process, and in that the advantages of mesoporous structure with appropriate pore size in metal-containing NPMC were elucidated for high-performance MEAs.

Onion-like Pt-terminated Pt–Cu bimetallic nano-sized electrocatalysts (Pt/Cu/Pt/C) were synthesized by using an electroless deposition method. The synthesized Pt/Cu/Pt/C consisted of a Pt-enriched shell, a sandwiched Pt–Cu alloy layer, and a Pt core. The Pt/Cu/Pt/C showed higher electrocatalytic activity toward oxygen reduction reaction in half-cell test than that of commercial Pt/C due to an electronic structure change in the Pt-enriched shell, resulting from the sandwiched Pt–Cu alloy layer underneath. The stability of the Pt/Cu/Pt/C was examined by using both half-cell and single-cell degradation tests. In both tests, the Pt/Cu/Pt/C exhibited stronger resistance to catalyst degradation than that of the commercial Pt/C. It is notable that cell performance with the Pt/Cu/Pt/C was fully recovered by N2 purging after single-cell degradation testing, indicating there was no permanent damage to the electrocatalyst during the test. It is suggested that thermodynamically-stable structure of the Pt/Cu/Pt/C contributed to the improved stability.

Electrochemical catalysts with a core-shell structure have received much attention because of their enhanced efficiency and activity. Among them, those with a CuPd alloy core exhibit better activity than the ones with a single metal Pd core, which is known to be an excellent core-material. However, the superior performance of previously reported Pt catalysts with CuPd core has only been observed in half-cells, and was not reflected or even expanded to single-cells. We report catalysts having a Matryoshka-like structure with a Pt outer-layer, Cu interlayer, and Pd core for oxygen reduction reaction. This catalyst has 3.4 times higher Pt mass activity than the commercial Pt/C in half-cells, and also performs better in single-cells at only 0.056 mgPt cm−2. Particularly, the stability of this catalyst satisfies the 2020 DOE target, and electrochemical surface area loss during the stability test is only 40 % for this catalyst, while that of Pt/C is 80 %.

The effect of an enlarged specific surface area of the membrane with well-defined line patterns on the performance of a direct methanol fuel cell (DMFC) is investigated and compared with the baseline pristine Nafion 115 membrane. Line patterns with dimensions ranging from several tens of nanometers to several micrometers were fabricated on Nafion 115 membranes with high reliability using thermal imprint lithography to ensure an uncollapsible structure. In the case of quasi-nano-patterned membrane the cell performance increased about 35% compared with that of the pristine Nafion 115 membrane owing to an increased effective three-phase boundary caused by an enlarged specific surface area. Thus the performance of DMFCs can be improved further by controlling the shape and size of the line patterns for sufficient formation of the three-phase boundary.

An inverse-opal poly(3,4-ethylene dioxythiophene) (PEDOT) electrode was fabricated by electrodeposition of EDOT onto a PEDOT:poly(styrene sulfonate) filler in a self-assembled polystyrene template. By this novel fabrication method, the inverse-opal electrode was directly assembled into a dye-sensitized solar cell (DSSC) as a Pt-free counter electrode without any additional processing. This inverse-opal PEDOT electrode exhibits superior electrocatalytic activity and easy electrolyte diffusion in the electrode, as the inverse-opal electrode provides a porous morphology. The improved reflectivity of the inverse-opal electrode was also observed in the incident-photon conversion-efficiency spectra at low wavelength, which was a characteristic of its well-ordered structure. Therefore, the inverse-opal PEDOT electrode could successfully act as an alternative counter electrode for DSSCs to replace Pt in the counter electrode.

a b s t r a c t Carbon-supported PtPdCo/C ternary electrocatalysts were prepared by using the sodium borohydride method for use as a cathode catalyst in direct methanol fuel cells (DMFCs). The electrocatalyst particles with a size of 2-3 nm were uniformly dispersed on carbon supports. PtPdCo/C showed a similar per- formance compared to commercial Pt/C in the oxygen reduction reaction (ORR) tests conducted with a rotating disk electrode (RDE). On the other hand, PtPdCo/C showed higher methanol tolerance than Pt/C in acidic media with methanol. In the single-cell tests, the performance of the PtPdCo/C electrocatalyst was approximately 50% higher than that of Pt/C owing to its enhanced methanol tolerance. In the long- term operation test with the single-cell, the maximum power density of PtPdCo/C decreased only by 14% from its initial value. These results indicate that the PtPdCo/C catalyst is potentially an alternative electrocatalyst for the cathode in DMFCs.

The integration of a gas diffusion layer with a flow-field is essential for enhancing the polymer electrolyte membrane fuel cell performance. This is achieved by exploiting the ability of a gas diffusion layer-flow-field combination to decrease the size of the reactant pathway and the thickness of the membrane-electrode assembly, thereby reducing electrical and mass transport resistance. This study proposes a unified membrane-electrode assembly that incorporates graphene foam that functions as both a flow-field and a gas diffusion layer. The unified membrane-electrode assembly exhibits higher performance than conventional membrane-electrode assembly on overall current densities region, which is attributed to the increased the pressure drop. Furthermore, its estimated volume power density can be increased because of the 82% decrease in its thickness. Also, the simulation results show that this design enhances the exchange current density due to pressure drop in the graphene foam.

Monodispersed hollow silica nanospheres were synthesized in a three step process of emulsion polymerization, the sol–gel reaction, and core dissolution. The physicochemical characteristics of the nanospheres were investigated by scanning electron microscopic, transmission electron microscopic, thermogravimetric, and nitrogen adsorption analyses. The average diameter of the hollow silica nanospheres was about 300 nm, and shell thickness was about 17 nm. In addition, the adsorption characteristics of bovine serum albumin (BSA) were evaluated in terms of initial concentration, contact time, pH, and temperature. Adsorption equilibrium and kinetic data were well explained in the entire experimental region by Langmuir isotherm and pseudo-second-order kinetic models, respectively. Our results show that the synthesized hollow silica nanospheres could be used as a good medium for BSA adsorption.

The durability of membrane electrode assemblies (MEAs) with varying amounts of Pt loading on the cathode of polymer electrolyte membrane fuel cells was investigated using load cycling as an accelerated degradation test (ADT). The single-cell performance of the MEA as determined by the ADT declined by approximately 34, 48, and 78%, when cathode Pt loading in the MEA was reduced to 0.3, 0.2, and 0.1 mg cm−2, respectively. The increase in MEA performance declined at higher cathode Pt loading conditions, and the degradation rate of MEA performance was also diminished. To characterize the electrochemical and structural properties of the MEAs, cyclic voltammograms, electrochemical impedance spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and field-emission scanning electron microscopy were utilized before and after ADT.

To understand the difference in degradation characteristics between carbon-supported platinum (Pt/C) and platinum–nickel alloy (Pt1Ni1/C) cathode catalysts in membrane electrode assemblies (MEAs) of a polymer electrolyte membrane fuel cell (PEMFC), constant current operation of MEA in a single cell was conducted for 1100 h. A significant change in cell potential for the Pt1Ni1/C MEA was observed throughout the test. High-resolution transmission electron microscopy showed that sintering and detachment of metal particles in the Pt1Ni1/C catalyst occurred more sparingly than in the Pt/C catalyst. Instead, X-ray photoelectron spectroscopy element mapping revealed dissolution of Ni atoms in the Pt1Ni1 catalysts even when the Pt1Ni1/C catalyst used in the MEA was well synthesized.

Capsaicin (8-methyl-N-vanillyl-6-nonenamide), a pungent ingredient of hot chili peppers, has been reported to possess substantial anticarcinogenic and antimutagenic activities. In the present study, we investigated the effect of capsaicin on induction of apoptosis in highly metastatic B16-F10 murine melanoma cells. Capsaicin inhibited growth of B16-F10 cells in a concentration-dependent manner. Proapoptotic effect of capsaicin was evidenced by nuclear condensation, internucleosomal DNA fragmentation, in situ terminal nick-end labeling of fragmented DNA (TUNEL), and an increased sub G1 fraction. Treatment of B16-F10 cells with capsaicin caused release of mitochondrial cytochrome c, activation of caspase-3, and cleavage of poly (ADP-ribose) polymerase in a dose-dependent manner. Furthermore, Bcl-2 expression in the B16-F10 cells was slightly down-regulated by capsaicin treatment. In contrast, there were no alterations in the levels of Bax in capsaicin-treated cells. Collectively, these findings indicate that capsaicin-induces apoptosis of B16-F10 melanoma cells via down-regulation the Bcl-2.

Hydrogen/deuterium (H/D) exchange studies that were monitored by liquid chromatography–electrospray ionization mass spectrometry (LC–ESIMS) were used to obtain a structural description of the compact acid-denatured state of ferricytochrome c (A-state). Due to the very different solvent conditions necessary to generate the nonnative states, it was essential that after deuterium labeling the nonnative states were refolded to the native state to insure high reproducibility during sample preparation and LC–ESIMS analysis. Approximately 30% lower deuterium was found incorporated in the A-state compared to the acid-denatured (U A ) state. The analysis of the width of the mass peak suggests that the distribution of conformers sampled in the A-state was relatively narrow and that the compactness of the A-state was much closer to that of the native state than to the acid-denatured state. The LC–ESIMS study of partially deuterium-labeled peptic fragments derived from the A-state conformer generated under H/D quenching conditions were interpreted in terms of a significant loss of structural integrity within amino acid region 22–46.