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To achieve a sustainable society, CO 2 emissions must be reduced and efficiency of energy systems must be enhanced. The polymer electrolyte membrane fuel cell (PEMFC) has zero CO 2 emissions and high effectiveness for various applications. A well-designed membrane electrolyte assembly (MEA) composed of electrode layers of effective materials and structure can alter the performance and durability of PEMFC. We demonstrate an efficient electrode deposition method through a well-designed carbon single web with a porous 3D web structure that can be commercially adopted. To achieve excellent electrochemical properties, active Pt nanoparticles are controlled by a nanoglue effect on a highly graphitized carbon surface. The developed MEA exhibits a notable maximum power density of 1082 mW/cm 2 at 80°C, H 2 /air, 50% RH, and 1.8 atm; low cathode loading of 0.1 mg Pt /cm 2 ; and catalytic performance decays of only 23.18 and 13.42% under commercial-based durability protocols, respectively, thereby achieving all desirables for commercial applications.

This review summarizes Cu-based catalysts for sustainable hydro-deoxygenation of glycerol to 1,2-propanediol with and without external hydrogen including various mechanistic pathways for the reactions involved.

To improve the sulfur tolerance of CeO2-supported Pt catalysts for water gas shift (WGS) using waste-derived synthesis gas, we investigated the effect of synthesis methods on the physicochemical properties of the catalysts. The Pt catalysts using CeO2 as a support were synthesized in various pathways (i.e., incipient wetness impregnation, sol-gel, hydrothermal, and co-precipitation methods). The prepared samples were then evaluated in the WGS reaction with 500 ppm H2S. Among the prepared catalysts, the Pt-based catalyst prepared by incipient wetness impregnation showed the highest catalytic activity and sulfur tolerance due to the standout factors such as a high oxygen-storage capacity and active metal dispersion. The active metal dispersion and oxygen-storage capacity of the catalyst showed a correlation with the catalytic performance and the sulfur tolerance.

Ammoxidation of m-xylene is evaluated in the presence of a customized heteropoly acid catalyst as an imidazole/molybdovanadophosphoric acid (imidazole/PMoV). Imidazole is employed to maintain its heterogeneous phase during the ammoxidation reaction and to provide the thermal stability of PMoV with the expectation that imidazole can generate strong electronic interactions with terminal molybdenum-oxygen on PMoV. The characterizations of the prepared catalysts are performed using SEM–EDX, XRD, FT-IR, Raman, XPS, and TGA to prove the physical and chemical changes by incorporating imidazole to PMoV, respectively. Also, the thermal stability of the developed catalyst is confirmed by the means of heat treatment test at relatively high temperature. The composite catalyst, imidazole/PMoV, shows an excellent conversion rate of over 98% with high selectivity of isophthalonitrile in m-xylene ammoxidation. Moreover, while the imidazole-free PMoV catalyst is deactivated and washed out during the reaction, the catalyst durability of the imidazole/PMoV is preserved without significant activity loss after 5 reaction cycles at 380 °C.

A detailed understanding of the catalytic upgrading of light cycle oil (LCO) is important to achieve effective deep hydrodesulfurization (HDS) when LCO is mixed with straight run gas oil in the diesel pool. Herein, HDS of polyaromatic-rich LCO was studied at the molecular level over three NiMo catalysts on silica–alumina supports, which were synthesized on the pilot scale using different silica/alumina mixing procedures. Gas chromatography with atomic emission detection and two-dimensional gas chromatography with time-of-flight mass spectrometry were used to evaluate the HDS performance through determining the feed and product compositions, respectively, at the molecular level. Furthermore, the textural properties of the catalysts were evaluated using Raman spectroscopy, transmission electron microscopy, and the temperature-programmed desorption of NH3. The performance of the best catalyst was attributed to its higher content of octahedrally coordinated Mo oxide species, a lower number of layered stacks, and the more acidic sites on the surface. In addition, the hydrotreating reactivity of various family groups in LCO over the catalyst was investigated.

Layered double hydroxides (LDHs) with two-dimensional nanostructure are inorganic materials that have attractive advantages such as biocompatibility, facile preparation, and high drug loading capacity for therapeutic bioapplications. Since the intercalation chemistry of DNA molecules into the LDH materials were reported, various LDH nanohybrids have been developed for biomedical drug delivery system. For these reasons, LDHs hybridized with numerous therapeutic agents have a significant role in cancer imaging and therapy with targeting functions. In this review, we summarized the recent advances in the preparation of LDH nanohybrids for cancer therapeutic strategies including gene therapy, chemotherapy, immunotherapy, and combination therapy.

The effect of the Au coated printed circuit board (PCB) as a current collector on the performance of fuel cells is demonstrated. In this study, optimized pulse electroplating was introduced, which was found to be much more effective compared to the direct current (DC) plating for the PCB fabrication based on the passive area from the potentiodynamic polarization scan. Variable electrochemical parameters such as applied potential and frequency for the pulse electroplating method are controlled. Using the polarization tests, the corrosion behavior of the Au coated PCB layer was also observed. From these basic data, the coating methods and electrochemical parameters were systematically controlled to achieve efficient results for direct methanol fuel cells (DMFCs). The stability test for the cell operation indicates that the micro DMFC with the Au coated PCB substrate formed at a frequency of 10 Hz exhibited the highest stability and performance. As a result, the Au coated PCB substrate using pulse electroplating at 1.5 V and 1 kHz can be a promising current collector for portable DMFCs.

Poly(ether imide) (PEI) membranes for polymer electrolyte membrane fuel cells (PEMFCs) are prepared by the electrospinning method. This approach produces a membrane with a high porosity and surface area that is suitable for accommodating proton-conducting materials. A composite membrane was prepared by impregnating the pores of the electrospun PEI membrane with Aquivion ionomer. Then, an inorganic proton conductor in the form of SiO2/heteropolyacid (HPA) nanoparticles was prepared by a microemulsion process and the particles added to the Aquivion ionomer. The membranes were characterized by field emission scanning electron microscopy (FE-SEM) and single-cell performance testing for PEMFC. The durability of the composite membrane was assessed via accelerated lifetime and on/off tests. The ionomer-impregnated electrospun PEI membrane showed good thermal stability, satisfactory mechanical properties, and high proton conductivity. The addition of the SiO2/HPA nanoparticles improved the proton conductivity of the composite membrane, thereby allowing the operating temperature in low humidity environments to be extended. The composite membrane exhibited promising properties for application in high-temperature PEMFCs.

We developed a new class of acid-base bifunctional heterogeneous catalyst, which can be used in the transesterification of rapeseed oil for highly efficient biodiesel production. A simple Keggin-type HPA (heteropoly acid) functionalization on the surface of zeolitic imidazolate framework-8 (ZIF-8) nanoparticles, through an imidazolium medium, results in the bifunctional heterogeneous catalysts. The hybrid materials exhibit a novel hierarchically core-shell nanostructure, which provides a large surface area and interconnectivity, leading to a thin-wrinkled HPA shell at the surface of rhombic dodecahedral ZIF-8 core crystals. A strong O N hybrid bonding through an electrostatic effect in the hybrid materials demonstrates a strong interaction between the Keggin and imidazole units, which is one of the main driving forces of hybrid materials formation. Additionally, the transformation of the HPA/ZIF-8 ratio in the hybrid materials changes the acidity and basicity, thereby affecting catalyst activity. We used these bifunctional core-shell materials as environmentally friendly heterogeneous catalysts in the transesterification of rapeseed oil with methanol to produce a high-quality biodiesel. Of particular interest, the HPA-functionalized ZIF-8 catalyst with a proper HPA/ZIF-8 ratio shows a high FAME conversion of 98.02% along with high recyclability because of the sufficiently large surface area and bi-functionality of strong acidity. Furthermore, the HPA-functionalized ZIF-8 catalyst shows a high reaction efficiency of the benzyl alcohol oxidation process, indicating a great potential of our catalyst to a wide range of applications.

Platinum functions exceptionally well as a nanoparticulate catalyst in many important fields, such as in the removal of atmospheric pollutants, but it is scarce, expensive and not always sufficiently durable. Here, we report a perovskite system in which 0.5 wt% Pt is integrated into the support and its subsequent conversion through exsolution to achieve a resilient catalyst. Owing to the instability of most Pt oxides at high temperatures, a thermally stable platinum oxide precursor, barium platinate, was used to preserve the platinum as an oxide during the solid-state synthesis in an approach akin to the Trojan horse legend. By tailoring the procedure, it is possible to produce a uniform equilibrated structure with active emergent Pt nanoparticles strongly embedded in the perovskite surface that display better CO oxidation activity and stability than those of conventionally prepared Pt catalysts. This catalyst was further evaluated for a variety of reactions under realistic test environments—CO and NO oxidation, diesel oxidation catalysis and ammonia slip reactions were investigated. Nanoparticulate platinum is a highly active catalyst, but it is scarce, expensive and not always sufficiently durable. Now, barium platinate has been used as a vehicle to preserve platinum as an oxide during the solid-state synthesis of a Pt-doped titanate perovskite; this enables the production of a structure with active and stable Pt nanoparticles on the perovskite surface that catalyses CO oxidation.

As the hydrogen economy is coming soon, the development of an efficient H2 production system is the first issue to focus on. In this study, a first attempt to utilize light cycle oil (LCO) feedstock is introduced for H2 production through autothermal reforming (ATR) using perovskite catalysts. From a careful characterization, it is found that LCO possesses a high content of C&ndash, H and S/N compounds with over 3&ndash, 4 ring bonds. These various compounds can directly cause catalyst deactivations to lower the capability of H2 extraction from LCO. To achieve a heteroatom resistance, two different perovskite micro-tubular catalysts are designed with a Ru substitution at the B-site. The activity and stability of the Ru doped perovskite were controlled by modifying the Ru electronic structure, which also affects the oxygen structures. The perovskite with a B-site of Cr reveals a relatively high portion of active Ru and O, demonstrating an effective catalyst structure with a comparable LCO reforming activity at the harsh ATR reaction conditions. The greater stability due to the Ru in the perovskite is investigated post-characterization, showing the possibility of H2 production by LCO fuel through the perovskite catalysts.

Biocompatible hydrotalcite nanohybrids, i.e., layered double hydroxide (LDH) based nanohybrids have attracted significant attention for biomedical functions. Benefiting from good biocompatibility, tailored drug incorporation, high drug loading capacity, targeted cellular delivery and natural pH-responsive biodegradability, hydrotalcite nanohybrids have shown great potential in drug/gene delivery, cancer therapy and bio-imaging. This review aims to summarize recent progress of hydrotalcite nanohybrids, including the history of the hydrotalcite-like compounds for application in the medical field, synthesis, functionalization, physicochemical properties, cytotoxicity, cellular uptake mechanism, as well as their related applications in biomedicine. The potential and challenges will also be discussed for further development of LDHs both as drug delivery carriers and diagnostic agents.

The catalytic combustion of soot and CO is one of the key technologies required to meet rigorous emission standards. Recently, solid solution materials have been employed in heterogeneous catalysts because of their remarkable intrinsic activities and good stabilities. However, the low number of contact points between soot particles and the catalyst remains a challenge to enhancing catalytic performance. Thus, we herein report the preparation of Ce-ZrO2 solid solution nano-fibrous web catalysts with a hierarchical structure using an electrospinning method, where Ag particles were loaded onto the surface of the Ce-ZrO2 webs. X-ray diffraction, scanning transmission electron microscopy, and energy dispersive spectroscopic studies allowed us to investigate the morphological and crystal structures of the prepared Ce-ZrO2 and Ag/Ce-ZrO2 web catalysts. Moreover, the relationship between the Ce/Zr ratio and activated oxygen is discussed based on X-ray photoelectron spectroscopy results. Following the catalytic oxidation of soot and CO using our novel materials, we found that the Ce0.67Zr0.33O2 web exhibited higher catalytic activities than the Ce0.5Zr0.5O2 and Ce0.33Zr0.67O2 webs, respectively. In addition, Ag/Ce0.67Zr0.33O2 exhibited enhanced catalytic activity compared with the pristine Ce0.67Zr0.33O2 for the oxidation of both soot (e.g., 500 °C vs. 544 °C at 50% conversion) and CO (e.g., 282 °C vs. 408 °C at 50% conversion). It therefore appeared that our proposed Ce-ZrO2 solid solution nano-fibrous web catalysts bearing Ag particles exhibited superior redox properties and enhanced surface areas, and as such, are promising candidates for use in the oxidation of both soot and CO.

The purpose of this work is to investigate proper hydrogen production methods from methane through the parametric study for the highly active and stable nanofibrous perovskite catalyst. A ruthenium doped lanthanide chromate (LaCr0.8Ru0.2O3) micro-fibrous perovskite catalyst is prepared and fixed to focus on the effect of reaction environments such as steam, partial oxidation and autothermal conditions. Temperatures, H2O/C and O2/C ratios were occasionally changed for the investigation of the effects and the optimization conditions. At the same perovskite catalyst system, the reaction at the autothermal atmosphere is the most effective conditions in terms of both CH4 conversion and H2 production, which was comparable to the theoretical calculations. It is found that conversion increases with oxygen at even low temperature while the H2 productivity increases with much stable behavior at steam condition. These are more obvious at the elevated temperature with each optimized H2O and O2 amounts for high activity by low activation energy. Time-on-stream runs conducted on these three reactions with each optimized conditions of 50 h at 800 °C, H2O/C = 3 and O2/C = 0.5. The perovskite micro-fiber catalyst at autothermal condition shows excellent CH4 conversion of over 95%, H2 production of around 70%, and even H2/CO of over 4. On the other hand, the reactivity at the steam condition is lower and even slow. The durability at the partial oxidation condition starts to decrease after 10 h due to the instability of the perovskite at the extremely oxidative concentration which causes a relatively high coke formation. Therefore, it is worthwhile in suggesting proper autothermal reaction conditions for the highly active and stable perovskite catalyst like LaCr0.8Ru0.2O3 micro-fibers.

An Aquivion/titanium zirconium oxide nanofibrous web composite membrane was prepared and tested as a proton exchange membrane in a hydrogen/air fuel cell. The incorporation of a small dose (9 wt % membrane) of a uniformly distributed electrospun titanium zirconium oxide (TiO2/ZrO2; Ti/Zr = 1:1 atomic ratio) nanofibrous web significantly improved hydromechanical stability of the composite membranes, which exhibited approximately 2 times higher water retention and 30 times lower dimensional change than a pristine Aquivion membrane under in-water membrane hydration conditions. Phosphate functionalities were successfully added onto the nanofiber surface, as confirmed by X-ray photoelectron spectroscopy (XPS) analysis. The added phosphate functionality resulted in higher proton conductivity of the prepared composite membrane compared to the non-modified TiO2/ZrO2 nanofibrous web composite membrane [e.g., 0.027 S cm–1 versus 0.021 S cm–1 at 120 °C and 40% relative humidity (RH)]. A single cell test also showed ...

Oxygen reduction reaction (ORR) activity and stability of the cathode catalyst are important issues for practical applications, which should be even considered for the materials in high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). To improve these properties, modification of the catalyst electronic structure and finding durable supports can be a good approach. In this study, we synthesized a noble nanofibrous composite electrode which consist of carbon nanotube (CNT)-winded Pt/TiO2 nanofiber (CNT-Pt/TiO2). Our approach takes advantages of the electrOchemical conductiVity of CNF as well as better stability from the corrosion resistivity of TiO2 and strong metal-support interaction (SMSI) between the Pt nanoparticles and TiO2 nanofibers for less Pt dissolution. We also found that the Pt electronic state can be changed by an interaction with neighbouring CNT and TiO2, resulting a decrease of Pt d-band vacancy for enhanced catalytic activity. Furthermore, nanofibrotis structure with a unique 3D pore structure provides higher surface area for additional improvements of the mass transfer. These results reveal that the CNT-Pt/TiO2 nanofiber based electrode shows enhanced performance with the maximum power density of 567 mW cm(-2) compare to commercial Pt/C (461 mW cm(-2)) with a significant durability at harsh conditions of 120 degrees C and RH 40%. Refereed/Peer-reviewed

Design of small-sized Au@Pt core-shell nanocatalysts with high activity and stability is crucial area for a wide range of electronic and chemical devices. Here, we report a novel reduction method using UV treatment at room temperature by a weak reducing agent of H 2 O 2 enabling to produce carbon-supported small Au nanoparticles as the core of Pt shells. Different thicknesses of Pt layers are deposited on the Au to configure small-sized core@shell nanocatalysts. We acquire superior catalytic activity of Au@Pt catalysts toward cyclic voltammetry analysis and oxygen reduction reaction (ORR) via atomic level control of the particle size and the electronic structure. Underlying mechanism of the ORR activity is described from the aspect of compressive strain caused by shorter Au-Au distance than the bulk counterpart. The thickness of the Pt shell is shown to play an important role in stabilizing the nanocatalyst. Using density functional theory (DFT) calculations we validate the experimental outcomes. Top-quality power density above 2 W cm −2 at low Pt loading (0.1 mg cm −2 ) is achieved by a bilayer small-size Au@Pt core-shell catalyst with an excellent durability over 10,000 cycles by ADT, which is, indeed, beyond the recent DOE targets for a proton exchange membrane fuel cell system.

A novel synthesis of morphology-controlled perovskite networked with LaCr 0.8 Ru 0.2 O 3 nanoparticles was introduced using activated carbons as sacrificial templates. These catalysts were used for the hydrogen production by heavy-hydrocarbon autothermal reforming. To investigate the effect of the carbon templates, morphology-controlled perovskites using activated carbons and a non-templated catalyst were prepared to determine how carbon templates influence the chemical structure of the perovskite. The carbon templates produced a crystalline structure with the well incorporation of Ru under mild calcination conditions. The morphology of the hollow fibers provided a higher specific surface area than that of the porous grain catalyst with a similar average particle size (∼80 nm). It was found that the hollow fibers showed a unique pore structure with large macropores from 1 to 100 μm, which might offer a higher surface area and enhanced mass transfer of the reactants. This provided a higher activation energy for H 2 production than the porous grain and non-templated catalysts during the autothermal reforming of heavy hydrocarbons. As a result, the fibrous feature and well-defined chemical structure were crucial factors when cracking the hydrocarbon chain. The hollow fiber catalyst showed high reforming efficiency for H 2 production (>65 mol%) from heavy-hydrocarbon fuels during long-term experiments, featuring substantial durability with low carbon deposition and no structural changes.

This research was supported by the New & Renewable Energy Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) with a financial resource from the Ministry of Trade, Industry & Energy (No. 20133030011320). An efficient cathode for solid oxide fuel cell (SOFC) is mainly determined by the oxygen reduction reaction (ORR) activity of the mixed materials. We demonstrate a new microstructure design through a nanofibrous electrode based on an unique corn-cob structure. One-step process to produce a corn-cob ceramic nanofiber of La0.8Sr0.2MnO3 (LSM) and Y2O3-stabilized ZrO2 (YSZ) is introduced by an electrospinning equipped with a coaxial nozzel. From the microscope analysis, perfect corn-cob nanofibers are finely produced with the diameter of 350 nm for a core and nanoparticles (30-40 nm) stacked on the surface like as a core-shell structure. The cathode fabricated by nanofibers with LSM outside and YSZ inside (YSZ@LSM) shows the best maximum power density of 1.15 Wcm-2 at 800 oC with low polarization resistance, which is higher than the reverse core and shell positions (LSM@YSZ) and even the commercial LSM-YSZ. This better outcome is more obvious at the elevated temperature due to the accelerated catalytic activity. Therefore, we could find the insight into the key factors enhancing the ORR activity and single cell performance in terms of not only the nanofibrous core@shell structure but also more reaction active sites from the optimum catalyst position at the designed corn-cob nanofibers based cathodes. Preprint Postprint

The toxic nature of acetaldehyde renders its removal from a wide range of materials highly desirable. Removal of low-concentration acetaldehyde (a group 1 carcinogenic volatile organic compound) using an adsorbent of cellulose-based activated carbon fiber modified by amine functional group (A@CACF-H) is proposed, using 2 ppm of acetaldehyde balanced with N2/O2 (79/21% v/v) observed under continuous flow, with a total flow rate of 100 mL/min over 50 mg of A@CACF-H. The effective removal of the targeted acetaldehyde is achieved by introducing the functionalized amine at optimized content. The removal mechanism of A@CACF-H is elucidated using two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (2D-GC TOF-MS), indicating the efficacy of the proposed acetaldehyde removal method.

Perovskite-type oxides have been widely applied in heterogeneous catalytic reactions, such as soot oxidation. However, a poor contact point between the catalyst and solid reactant (soot) often limits the catalytic performance. Here, we report La 1 − x Sr x Co 0.2 Fe 0.8 O 3 − δ perovskite oxide catalysts with a unique three-dimensional (3D) fiber web structure that increases the high-contact area by trapping soot in the unique pore structure for effective catalytic activity. This feature was carefully analyzed using scanning transmission electron microscopy (STEM) tomography to investigate the location of the soot on the web. The structure of the web, with a thickness of approximately 55 μm, indicated that the soot particles were caught by the 3D pores between the fibers. The relationship between the Sr amount and activate oxygen was also characterized by means of XPS. The results show that the Sr amount of 0.4 produced the highest amount of active oxygen species (O − ) that are essential for soot oxidation reaction. The developed catalyst exhibited a good catalytic performance due to the optimized perovskite chemical structure and the greatly increased number of the contact points owing to the 3D inter-fiber spaces. Hence, our proposed approach is reasonable for application to real soot combustion processes and can also be easily extended to numerous other catalytic processes to enhance the catalytic activity.

As a new carbon support for high temperature – proton exchange membrane fuel cell (HT-PEMFC), the nitrogen doped CNF/ACF (N/CNF/ACF) was synthesized by coating and annealing the polypyrrole to the surface of carbon nanofiber (CNF) grown on activated carbon fiber (ACF). The durability and electrochemical performance of Pt/N/CNF/ACF and commercial Pt/C was examined and compared with various analytical tools as well as accelerated life-time test (ALT) at high temperature of 120 °C. The catalytic durability on Pt/N/CNF/ACF was improved due to the enhanced π-bonding and the basic electron donor property of nitrogen contents. Such stability of Pt/N/CNF/ACF was originated from the strong interaction between Pt particles and carbon matrix with nitrogen contents. The evidences on the nitrogen effect of Pt/N/CNF/ACF were elucidated with the gentle loss of electrochemical active surface area (ECSA) and the shift of XPS peak (Pt 4f) to the direction of higher binding energy, comparing with those of commercial Pt/C, before and after ALT. The physical and chemical properties on the Pt/N/CNF/ACF was characterized with HR-TEM, FE-SEM, FT-IR, XRD and XPS, in detail. And, their electrochemical properties for HT-PEMFC were examined with single cell and half cell test, before and after ALT.

The particle size effect of N-doped mesoporous carbon was investigated for ORR activity in acid condition and for issue of a mass transfer and gas diffusion in PEMFCs. As for a non-Pt ORR catalyst, nitrogen (N)-doped ordered mesoporous carbons (OMCs) with a various particle sizes with the range of the average 20, 45 and 75 μm were synthesized by the precursor of polyaniline for the N/C species, and a mesoporous silica template was used for the physical structure for preparation of nitrogen doped OMCs. The N-doped mesoporous carbons are promoted by a transition metal (Fe) to improve catalytic activity for ORR in PEMFCs. All the prepared carbons were characterized by via scanning electron microscopy (SEM), and to evaluate the activities of synthesized doped carbons, linear sweep was recorded in an acidic solution to compare the ORR catalytic activities values for the use in the PEMFC system. The surface area and pore volume were increased as the particles decreased, which was effective for the mass transfer of the reactant for higher activity at the limiting current regions.

Ethylbenzene (EB) and p-xylene (PX) are important chemicals for the production of industrial materials; accordingly, their efficient separation is desired, even though the difference in their boiling points is very small. This paper describes the efforts toward the identification of high-performance extractive agents for EB and PX separation by distillation. Most high-performance extractive agents contain halogen atoms, which present health hazards and are corrosive to distillation plates. To avoid this disadvantage of extractive agents, we developed a quantitative structure–relative volatility relationship (QSRVR) model for designing safe extractive agents. We have previously developed and reported QSRVR models for single extractive agents. In this study, we introduce extended QSRVR models for binary and ternary extractive agents. The QSRVR models accurately predict the relative volatilities of binary and ternary extractive agents. The service to predict the relative volatility for binary and ternary extractive agents is freely available from the Internet at http://qsrvr.opengsi.org/.

Nitrogen (N)-doped ordered mesoporous carbons (OMCs) with a dual transition metal system were synthesized as non-Pt catalysts for the ORR. The highly nitrogen doped OMCs were prepared by the precursor of ionic liquid (3-methyl-1-butylpyridine dicyanamide) for N/C species and a mesoporous silica template for the physical structure. Mostly, N-doped carbons are promoted by a single transition metal to improve catalytic activity for ORR in PEMFCs. In this study, our N-doped mesoporous carbons were promoted by the dual transition metals of iron and cobalt (Fe, Co), which were incorporated into the N-doped carbons lattice by subsequently heat treatments. All the prepared carbons were characterized by via transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). To evaluate the activities of synthesized doped carbons, linear sweep was recorded in an acidic solution to compare the ORR catalytic activities values for the use in the PEMFC system. The dual transition metal promotion improved the ORR activity compared with the single transition metal promotion, due to the increase in the quaternary nitrogen species from the structural change by the dual metals. The effect of different ratio of the dual metals into the N doped carbon were examined to evaluate the activities of the oxygen reduction reaction.

Dry reforming, a technique to combine methane and carbon dioxide, has received significant attention in efforts to produce synthesis gas (carbon monoxide and hydrogen). These gases can subsequently be used for C1 chemistry applications, and even for high-temperature fuel cell devices. However, suitable electrode materials with highly active and stable properties remain to be found for efficient utilization of a C1 fuel-based fuel cell system. A promising electrode material of yttria-doped strontium titanium oxide with trace ruthenium (Sr0.92Y0.08Ti0.98Ru0.02O3+/−δ; SYTRu) was developed in this work for an efficient and stable dry-reforming catalyst and compared to a Ru-loaded SYT (Ru/SYT) catalyst. The substituted Ru in the former sample was uniformly incorporated (primarily in the atomic level) in the SYT lattice with a perovskite structure. Different Ru species were observed in this case, unlike in the Ru/SYT sample. Ru doping decreased the oxygen vacancy formation energy in calculated by density functional theory and led to a high activity for the surface oxygen. The surface oxygen donating ability to the catalyst was responsible for facilitating the dissociation and decomposition of CH4 and CO2. This led to high conversion efficiency, good syngas selectivity, and stability, along with a small amount of coke formation.

Well-designed electronic configurations and structural properties of electrocatalyst alter the activity, stability, and mass transport for enhanced catalytic reactions. We introduce a nanofibrous oxide–carbon composite by an in situ method of carbon nanofiber (CNF) growth by highly dispersed Ni nanoparticles that are exsoluted from a NiTiO3 surface. The nanofibrous feature has a 3D web structure with improved mass-transfer properties at the electrode. In addition, the design of the CNF/TiO2 support allows for complex properties for excellent stability and activity from the TiO2 oxide support and high electric conductivity through the connected CNF, respectively. Developed CNF/TiO2–Pt nanofibrous catalyst displays exemplary oxygen-reduction reaction (ORR) activity with significant improvement of the electrochemical surface area. Moreover, exceptional resistance to carbon corrosion and Pt dissolution is proven by durability-test protocols based on the Department of Energy. These results are well-reflected t...

A bench-scale ammoxidation reaction of m-xylene was evaluated in the presence of V2O5/γ-Al2O3 catalyst. The experiment was performed in a packed-bed reactor with 25 mm i.d. using 200 g of catalyst. To alleviate sudden temperature hikes during ammoxidation, molten salt system was carefully built in the outer part of the reactor in a jacket-type. Higher value of heat capacity of molten salt led to the stabilized reaction temperature within tolerable ranges without significant deactivation of catalytic activity. Isophthalonitrile (IPN) was a main product to compare reaction performance, while m-tolunitrile, even hardly observed in a lab-scale experiment, was a noticeable by-product in this study. Reaction parameters include reaction temperature, oxygen to m-xylene ratio, NH3 to m-xylene ratio, and gas hourly space velocity. The selectivity of IPN over m-tolunitrile was clearly improved when reaction temperature was raised from 320 to 380 °C. For a long-term test, the reaction was evaluated in the period of one year. The catalyst was characterized before and after the long-term experiment and its changes were analyzed by N2-physisorption, SEM, XRD and XPS.

The vanadium redox flow battery (VRB) is an attractive energy storage technology due to its great advantages such as high energy efficiency and long life cycle. A carbon electrode has been commonly used as the electrode material for the VRB system. In this study, the effects of microwave treatment on the carbon electrode for the VRB are investigated under different microwave powers (0, 500, and 650 W). The microwave-treated carbon electrode is about twice as large as the pristine carbon electrode in specific surface area, showing about 2.72, 4.46, and 4.63 m2 g−1 at 0, 500, and 650 W, respectively. The oxygen-containing functional groups such as CO, CO, and OCO, which can promote the redox reactions in the VRB system, are also increased by the microwave treatment. When the microwave-treated carbon electrode is applied as the positive electrode for the VRB system, the coulomb, voltage, and energy efficiencies are enhanced. Thus, the microwave treatment can be a simple and effective method to prepare the carbon electrode for the VRB system.

Durability of high temperature fuel cells with low humidity has been receiving attention for its commercialization into the automobile. Therefore, advanced durability protocols are designed to evaluate the membrane electrode assembly (MEA) composed of short-side-chain conducting polymer (Aquivion™) at the high temperature of 120 °C and low humidity of 40%RH. Accelerated life time tests (ALTs) of on–off cycle test with the duration time of 10 min and load cycle test with a voltage sweep of 0.6 V–1.0 V and a duration of 4.25 min, are developed to induce different stresses. The different degradation behaviors of the MEAs are monitored and compared to the normal constant voltage mode of 0.6 V. The decay rate using the on–off cycle test is 0.113 mA/(cm2 min) whereas a slightly slower decay rate of 0.096 mA/(cm2 min) is obtained for the load cycle test. The electrochemical analyses of membrane electrode assembly (MEA) are confirmed periodically during the tests for each protocol using polarization curve, impedance spectroscopy and cyclic voltammetry. The characterizations of the MEA are carried out before and after the durability tests to verify the material degradation and failure mechanisms. Although both protocols show similar degradation on the MEA materials, the membrane degradation is more dominant after the on–off test while more catalyst degradation is observed after the load cycling test. Nafion® is also tested by the developed load cycle test to observe the difference between short-side-chain and long-side-chain conducting polymer.

The purpose of this work is to identify new accelerated life-time (ALT) test protocols for polymer electrolyte membrane fuel cell (PEMFC), which function at conditions of high temperature and low humidity (under 120 °C 40%RH). A design of accelerated life protocols was studied to observe degradation phenomena under different load step cycling conditions, compared with the constant voltage test at 0.6 V. The effects of changes in frequency and potential range are explored, and different degradation rates are revealed. The test protocol of constant voltage test, load step cycling and with different potential range show total performance decay rates of 5.3 mA·cm −2 ·h −1 , 8.4 mA·cm −2 ·h −1 and 10.2 mA·cm −2 ·h −1 , respectively, while the highest total decay rate of load step cycling with frequency change is 17.0 mA·cm −2 ·h −1 including a rapid decrease of current density after 450 cycles under 120 °C 40%RH. In respect to the operation of 500 cycles (35 h), material degradation failure mechanisms are investigated according to the electro- and physico-chemical characteristics of the MEA. The performances assessed by the life-time evaluation methods are strongly related to the increase in the membrane resistance and the release of the sulfate and fluoride ions, dominated more at a higher cycling frequency. Furthermore, in the contrast to the starting MEA, Pt aggregations of the catalysts and a decline in the electrochemical surface area (ECSA) are clearly observed at the end of the testing especially with a wider sweeping range, corresponded to the decrease in the electrochemical properties.

Demonstrated herein is a novel and easily controllable method using direct microwave irradiation treatment to enhance the electrochemical structure in the membrane electrode assembly (MEA) of the fuel cell. Through direct microwave irradiation, it is found that the pore dimension changed to an improved micropore structure with a 1.5-fold larger surface area (from 9.68 to 15.21 m 2 g −1 ) at the microwave power of 500 W than the rare statement, which is proportional to the mass/heat transfer properties, along with the higher interfacial site area in the electrode, for better electrochemical properties. This upgraded structure also increases the Pt catalyst utilization and reduces the electrical loss by increasing the ionic conductivity between the catalyst layer and membrane when combined with polymer electrolyte, a catalyst, and the Nafion membrane in MEA. Due to the enhancement of the MEA properties, the fuel cell performances of the microwave-irradiated MEAs show a significant improvement to 1.87 A cm −2 at 0.6 V over the conventional MEA performance of 1.47 A cm −2 . Especially achieved is a 110% enhancement in the limiting current density resulting from the developed electrochemical micropore structure.

a b s t r a c t In this study, a new type of carbon support materials for proton exchange membrane fuel cells (PEMFCs) was evaluated. Carbon nanofibers (CNFs) grown on activated carbon fibers (ACFs) were prepared through catalytic growth to yield CNF/ACF materials. CNFs were synthesized by using CH4 with Ni catalysts dis- persed on ACFs. The as-prepared samples were characterized with transmission electron microscopy (TEM) and scanning electron microscopy (SEM). SEM images revealed a three-dimensional CNF network grown on the ACF surface. High-temperature treatment effectively reinforced the CNF/ACF structure and led to increased electrochemical performance and durability of Pt catalysts in PEMFC operations. The accelerated degradation test (ADT) was used for stability evaluations of Pt catalysts. The ECSA loss from heat-treated Pt/CNF/ACF at 900 ◦ C was calculated to be 39.1%, whereas the ECSA loss from the non-heat- treated Pt/CNF/ACF rose to 56.3%. The results suggest that the higher corrosion resistance of the carbon support could come from the higher degree of graphitization through high-temperature heat treatment of CNF/ACF. This unique structure of the CNF grown on ACF can supply effective anchor sites for the stabilization of Pt particles. As a result, the heat-treated CNF/ACF is expected to be a promising carbon support to improve the cell performances of PEMFCs.

We report on polymer electrolyte membrane fuel cells (PEMFCs) that function at high temperature and low humidity conditions based on short-side-chain perfluorosulfonic acid ionomer (SSC-PFSA). The PEMFCs fabricated with both SSC-PFSA membrane and ionomer exhibit higher performances than those with long-side-chain (LSC) PFSA at temperatures higher than 100 °C. The SSC-PFSA cell delivers 2.43 times higher current density (0.524 A cm −1 ) at a potential of 0.6 V than LSC-PFSA cell at 140 °C and 20% relative humidity (RH). Such a higher performance at the elevated temperature is confirmed from the better membrane properties that are effective for an operation of high temperature fuel cell. From the characterization technique of TGA, XRD, FT-IR, water uptake and tensile test, we found that the SSC-PFSA membrane shows thermal stability by higher crystallinity, and chemical/mechanical stability than the LSC-PFSA membrane at high temperature. These fine properties are found to be the factor for applying Aquivion™ E87-05S membrane rather than Nafion ® 212 membrane for a high temperature fuel cell.

Extractive distillation is a highly effective process for the separation of compound pairs having low relative volatility values, such as ethylbenzene (EB) and p-xylene (PX) mixtures. Many solvents...