Synergistic growth of nickel and platinum nanoparticles via exsolution and surface reaction

Bimetallic catalysts combining precious and earth-abundant metals in well designed nanoparticle architectures can enable cost efficient and stable heterogeneous catalysis. Here, we present an interaction-driven in-situ approach to engineer finely dispersed Ni decorated Pt nanoparticles (1-6 nm) on perovskite nanofibres via reduction at high temperatures (600-800 oC). Deposition of Pt (0.5 wt%) enhances the reducibility of the perovskite support and promotes the nucleation of Ni cations via metal-support interaction, thereafter the Ni species react with Pt forming alloy nanoparticles, with the combined processes yielding smaller nanoparticles that either of the contributing processes. Tuneable uniform Pt-Ni nanoparticles are produced on the perovskite surface, yielding reactivity and stability surpassing 1 wt.% Pt/γ-Al2O3 catalysts for CO oxidation. This approach heralds the possibility of in-situ fabrication of supported bimetallic nanoparticles with engineered compositional distributions and performance.

Bifunctional 1,2,4-Triazole/12-Tungstophosphoric Acid Composite Nanoparticles for Biodiesel Production

Here, a composite nanoparticle with an acid-base bifunctional structure has been reported for the transesterification of rapeseed oil to produce biodiesel. Triazole-PWA (PWA = 12-tungstophosphoric acid) composite materials with a hexahedral structure are produced using the precipitation method, showing the average particle diameters of 200-800 nm. XPS and FT-IR analyses indicate well-defined chemical bonding of triazole moieties to the PWA. The functionalization and immobilization of PWAs are investigated due to strong interactions with triazole, which significantly improves the thermal stability and even surface area of the heteropoly acid. Furthermore, various ratios of triazole and PWAs are examined using NH₃-TPD and CO₂-TPD to optimize the bi-functionality of acidity and basicity. The prepared nanomaterials are evaluated during the transesterification of rapeseed oil with methanol to analyze the effect of triazole addition to PWAs according to the different ratios. Overall, the bifunctional triazole-PWA composite nanoparticles exhibit higher fatty acid methyl ester (FAME) conversions than pure PWA nanoparticles. The optimized catalyst with a triazole:PWA ratio of 6:1 exhibits the best FAME-conversion performance due to its relatively large surface area, balance of acidity, and strong basicity from the well-designed chemical nano-structure.

Nano-Composite Filler of Heteropolyacid-Imidazole Modified Mesoporous Silica for High Temperature PEMFC at Low Humidity

Nano-composite filler has received attention for the application to high temperature and low humidity polymer electrolyte membrane (PEM) in fuel cell systems. Heteropolyacids (HPAs) are one of the most attractive materials because of their conductive and thermally stable properties, but have practical limitations due to their high solubility. We investigated the stabilization of HPA on imidazole modified mesoporous silica as a nano-composite filler. The role of mesoporous silica as a support for imidazole and the distribution of chemically bonded HPA on the surface were both confirmed through physical and chemical analysis. The developed nano-composite was utilized to a PEM as a proton conducting filler, cast with commercial Aquivion^TM solution. Changing the HPA: imidazole ratio and HPA wt%, the composite membrane of Im10/PWA6/Si-MCM-41 (PWA 10 wt%) resulted in higher proton conductivity compared to the non-modified membrane at all operation conditions, especially at high temperature (140 °C) and low relative humidity (RH 10%), with values of 0.3530 and 0.0241 S/m, respectively. A single cell test at H₂/Air also showed the effect of adding the nano-composite filler at a wide range of temperatures, which outperformed a single cell with a pristine membrane even at an extremely low humidity condition.

Oxide-Carbon Nanofibrous Composite Support for a Highly Active and Stable Polymer Electrolyte Membrane Fuel-Cell Catalyst

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 to the single-cell tests with even-better performance at the kinetic zone compared to the commercial Pt/C under different operation conditions. CNF/TiO₂-Pt displays an enhanced active state due to the strong synergetic interactions, which decrease the Pt d-band vacancy by electron transfer from the oxide-carbon support. A distinct reaction mechanism is also proposed and eventually demonstrates a promising example of an ORR electrocatalyst design.

Selective Ion Transporting Polymerized Ionic Liquid Membrane Separator for Enhancing Cycle Stability and Durability in Secondary Zinc-Air Battery Systems

Rechargeable secondary zinc-air batteries with superior cyclic stability were developed using commercial polypropylene (PP) membrane coated with polymerized ionic liquid as separators. The anionic exchange polymer was synthesized copolymerizing 1-[(4-ethenylphenyl)methyl]-3-butylimidazolium hydroxide (EBIH) and butyl methacrylate (BMA) monomers by free radical polymerization for both functionality and structural integrity. The ionic liquid induced copolymer was coated on a commercially available PP membrane (Celguard 5550). The coat allows anionic transfer through the separator and minimizes the migration of zincate ions to the cathode compartment, which reduces electrolyte conductivity and may deteriorate catalytic activity by the formation of zinc oxide on the surface of the catalyst layer. Energy dispersive X-ray spectroscopy (EDS) data revealed the copolymer-coated separator showed less zinc element in the cathode, indicating lower zinc crossover through the membrane. Ion coupled plasma optical emission spectroscopy (ICP-OES) analysis confirmed over 96% of zincate ion crossover was reduced. In our charge/discharge setup, the constructed cell with the ionic liquid induced copolymer casted separator exhibited drastically improved durability as the battery life increased more than 281% compared to the pure commercial PP membrane. Electrochemical impedance spectroscopy (EIS) during the cycle process elucidated the premature failure of cells due to the zinc crossover for the untreated cell and revealed a substantial importance must be placed in zincate control.

Synthesis and application of hexagonal perovskite BaNiO3 with quadrivalent nickel under atmospheric and low-temperature conditions

A hexagonal perovskite BaNiO3 with unusually high-valence nickel(iv) was synthesized under atmospheric and low-temperature conditions by an ethylenediamine-derived wet-chemical route. Secondary phases disappeared with increase in the pH value, and the single-phase BaNiO3 was successfully synthesized at pH 10. The specific surface area was ∼32 m(2) g(-1), which is significantly enhanced compared to the BaNiO3 (0.3 m(2) g(-1)) synthesized by flux-mediated crystal growth. The BaNiO3 was used as an oxygen-evolution reaction (OER) catalyst, and the specific mass activity was ∼5 times higher than that of the BaNiO3 synthesized by flux-mediated crystal growth. As a result, the ethylenediamine-derived sol-gel synthesis could be a simple technique to prepare crystalline compounds such as perovskites and spinels, with unusually high-valence transition metals.

Interface-designed Membranes with Shape-controlled Patterns for High-performance Polymer Electrolyte Membrane Fuel Cells

Polymer electrolyte membrane fuel cell is a promising zero-emission power generator for stationary/automotive applications. However, key issues, such as performance and costs, are still remained for an economical commercialization. Here, we fabricated a high-performance membrane electrode assembly (MEA) using an interfacial design based on well-arrayed micro-patterned membranes including circles, squares and hexagons with different sizes, which are produced by a facile elastomeric mold method. The best MEA performance is achieved using patterned Nafion membrane with a circle 2 μm in size, which exhibited a very high power density of 1906 mW/cm² at 75 °C and Pt loading of 0.4 mg/cm² with 73% improvement compared to the commercial membrane. The improved performance are attributed to the decreased MEA resistances and increased surface area for higher Pt utilization of over 80%. From these enhanced properties, it is possible to operate at lower Pt loading of 0.2 mg/cm² with an outstanding performance of 1555 mW/cm² and even at air/low humidity operations.

Direct spun aligned carbon nanotube web-reinforced proton exchange membranes for fuel cells

A composite membrane prepared by electrospinning SPEEK and direct spinning of CNTs is more robust than SPEEK alone and outperforms SPEEK and Nafion 212 membranes.

Fabrication of electrospun SiC fibers web/phenol resin composites for the application to high thermal conducting substrate

Polycabosilane (PCS) could be spun to form fiber web by electrospinning PCS solution in 30% dimethylformide (DMF)/toluene solvent at 25 kV. The electrospun web is stabilized at 200 degrees C for 1 hour to connect fibers by softening PCS webs and pyrolysed to synthesize silicon carbide (SiC) webs at 1800 degrees C. The pyrolysis at 1800 degrees C increased the SiC crystal size to 45 nm from 3 nm at 1300 degrees C. However, the pyrolysis at 1800 degrees C forms pores on the surface of SiC fibers due to oxygen evaporation generated during thermals curing. SiC/phenol composite webs could be fabricated by infiltration of phenol resin and hot pressing. The thermal conductivity measurement indicates that higher SiC fibers filler contents increase the thermal conductivity up to 1.9 W/mK for 40% fraction of filler contents from 0.5 W/mK for 20% fraction of filler.

Pt nanoparticle-reduced graphene oxide nanohybrid for proton exchange membrane fuel cells

A platinum nanoparticle-reduced graphene oxide (Pt-RGO) nanohybrid for proton exchange membrane fuel cell (PEMFC) application was successfully prepared. The Pt nanoparticles (Pt NPs) were deposited onto chemically converted graphene nanosheets via ethylene glycol (EG) reduction. According to the powder X-ray diffraction (XRD) pattern and transmission electron microscopy (TEM) analysis, the face-centered cubic Pt NPs (3-5 nm in diameter) were homogeneously dispersed on the RGO nanosheets. The electrochemically active surface area and PEMFC power density of the Pt-RGO nanohybrid were determined to be 33.26 m2/g and 480 mW/cm2 (maximum values), respectively, at 75 degrees C and at a relative humidity (RH) of 100% in a single-cell test experiment.

Sepiocite, sepiolite-like nanoclay derived from hydrotalcite-like layered double hydroxide

Sepiocite, a synthetic sepiolite-like nanoclay, was derived from hydrotalcite-like Mg2Al(CO3)0.5-layered double hydroxide (LDH) under phase transformation at 270 +/- 3 degrees C. The crystal structure of sepiocite is conceptually very similar to that of sepiolite derived from montmorillonite clay because sepiocite is formed through the alternation of the blocks and tunnels along the crystallographic c-axis, with a partial dehydroxylation of the octahedral Mg-(OH)-Al configuration into tetrahedral ones. Three important findings regarding sepiocite were arrived at: (i) its high specific surface area of 128.25 m2/g with an average particle size of 200 nm, which is approimately equal to 3.5 times larger than the specific surface area of the pristine LDH (34.21 m2/g); (ii) its non-swelling property; and (iii) its strongly reduced anion-exchange capacity.

UV screening of ferulic acid-zinc basic salt nanohybrid with controlled release rate

Ferulic acid (FA), an organic UV absorber and free radical scavenger, was intercalated into an inorganic zinc basic salt (ZBS) matrix to prepare a UV screening material. FA molecules were vertically oriented bilayer in the ZBS lattice with an expansion of approximately 22.7 angstroms along the c-axis. The FA-ZBS nanohybrid exhibited a superior UV-A approximately UV-B screening ability and an antioxidant activity that was comparable to that of a pure FA molecule. The in vitro release test showed the biphasic release of the FA molecules from the FA-ZBS nanohybrid that consisted of an initial burst, followed by a slow and sustained release.

Fe3O4@polypyrrole core-shell nanohybrid for efficient DNA retrieval

Core-shell nanohybrid, Fe3O4@PPY, which consists of superparamagnetic Fe3O4 core and DNA attractive polypyrrole, was successfully synthesized through the free radical polymerization. The DNA retrieval efficacy of the nanohybrid was found to be very high in DNA solution with low concentration (approximately 33% uptake in 100 microM).

Effect of metal and glycol on mechanochemical dechlorination of polychlorinated biphenyls (PCBs)

This paper assesses the potential of mechanochemical method with fine metal powder, glycol and alkali for polychlorinated biphenyls (PCBs) removal from waste insulating oil. The effects of relevant parameters, such as kinds of chemicals, rate and time of milling were examined. After each run, the total PCBs content in waste insulating oil was measured. Polyethylene glycol 200, long chain-glycol was more effective than triethylene glycol and ethylene glycol, short chain-glycol as hydrogen donor in mechanochemical dechlorination of PCBs. A maximum of 99.9% PCBs removal (below 2 ppm) and 94% total chlorine removal were achieved with the mechanochemical process for 2 h.