Buckypaper-based catalytic electrodes for improving platinum utilization and PEMFC's performance

Prudent Practices in ex situ Durability Analysis Using Cyclic Voltammetry for Platinum-based Electrocatalysts

Platinum (Pt)-based electrocatalysts are at the vanguard of research initiatives to meet activity and durability targets for promoting large-scale adoption of fuel cell vehicles. Ex situ characterization of electrocatalyst activity and durability using cyclic voltammetry (CV) has a steep learning curve. Thus, many researchers who do not receive formal training in electrochemistry are left unsure how to proceed. Herein, we identify and compile prudent practices for reliable assessment of ECSA values with examples from our research on nanoscale catalytic films formed by the self-terminating electrodeposition of Pt. Starting with a conceptual framework to understand typical features in the CV of reversible redox couples, we present prudent practices in acquiring CV data aimed at nonelectrochemists. We then highlight specific features related to ECSA computation from Pt CV. Finally, we suggest safeguards that help avoid missteps and achieve repeatable results while conducting ex situ durability tests that extend over days.

Mechanically Robust Magnetic Carbon Nanotube Papers Prepared with CoFe2O4 Nanoparticles for Electromagnetic Interference Shielding and Magnetomechanical Actuation

The introduction of inorganic nanoparticles into carbon nanotube (CNT) papers can provide a versatile route to the fabrication of CNT papers with diverse functionalities, but it may lead to a reduction in their mechanical properties. Here, we describe a simple and effective strategy for the fabrication of mechanically robust magnetic CNT papers for electromagnetic interference (EMI) shielding and magnetomechanical actuation applications. The magnetic CNT papers were produced by vacuum filtration of an aqueous suspension of CNTs, CoFe₂O₄ nanoparticles, and poly(vinyl alcohol) (PVA). PVA plays a critical role in enhancing the mechanical strength of CNT papers. The magnetic CNT papers containing 73 wt % of CoFe₂O₄ nanoparticles exhibited high mechanical properties with Young's modulus of 3.2 GPa and tensile strength of 30.0 MPa. This magnetic CNT paper was successfully demonstrated as EMI shielding paper with shielding effectiveness of ∼30 dB (99.9%) in 0.5-1.0 GHz, and also as a magnetomechanical actuator in an audible frequency range from 200 to 20 000 Hz.

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.

Hierarchically structured catalyst layer for the oxygen reduction reaction fabricated by electrodeposition of platinum on carbon nanotube coated carbon fiber

Hierarchically structured fuel cell cathode catalysts consisting of Pt-nanoparticle clusters coated on a CNT-based, ORR active catalyst support were synthesized.

Biocatalytic carbon nanotube paper: a ‘one-pot’ route for fabrication of enzyme-immobilized membranes for organophosphate bioremediation

A generic methodology for a rapid and direct fabrication of enzymatically-active carbon nanotubes (CNTs) paper for organophosphates bioremediation is presented. The enzyme organophosphate hydrolase is immobilized onto CNTs simultaneously to membrane formation process.

Structural Properties of Chemically Functionalized Carbon Nanotube Thin Films

Buckypapers are thin sheets of randomly entangled carbon nanotubes, which are highly porous networks. They are strong candidates for a number of applications, such as reinforcing materials for composites. In this work, buckypapers were produced from multiwall carbon nanotubes, pre-treated by two different chemical processes, either an oxidation or an epoxidation reaction. Properties, such as porosity, the mechanical and electrical response are investigated. It was found that the chemical pretreatment of carbon nanotubes strongly affects the structural properties of the buckypapers and, consecutively, their mechanical and electrical performance.

Structure and Composition of Supported PtCu-LaO_x Composite Multi-Layer Membrane Electrode

In order to reduce production cost of Fuel Cells, a new type of Pt/C membrane electrodes -- PtCu-LaOx, LaOx-PtCu and PtCu-LaOx-PtCu composite multi-layer membrane electrodes -- would be raised, in which with developing different membranous layer form dispersed on the surface of carbonaceous or monocrystalline silicon substrates were manufactured by Ion Beam Sputtering technology. Phase composition, micro-area surface topography and elements of these electrodes were analyzed by X-ray Diffraction, Scanning Electron Microscopy combined with Energy Dispersive Spectrometry and Atomic Force Microscope, respectively. It was found that doping La could not only enhance Pt crystallization and decrease Pt grain size but also contribute to Pt(111) preferential orientation growing in the LaOx-PtCu, and that biggish ratio of La(At%) : Pt(At%) in micro-area would be difficult of occurring particles reunion on PtCu-LaOx surface, and that the orientation growing of Pt(200), Pt(220) and Pt(311) would be restrained in PtCu-LaOx and PtCu-LaOx-PtCu, and that the Pt alloy particle exhibited more homogeneous distribution and less size in PtCu-LaOx-PtCu. Our study indicated that these new types of membrane electrodes could be used in Fuel Cells and make Fuel Cells as a new power source for electrical vehicles.