Conventional detection of 2,4-dinitrophenol using quartz crystal microbalance

We present conventional detection of 2,4-dinitrophenol (DNP) for using the competitive reaction between DNP and DNP-conjugated albumin onto DNP antibody immobilized quartz crystal microbalance (QCM). This QCM method allows detection of DNP concentration in the range of 0.01 to 100 ng/ml; linear correlation obtains DNP concentration from 1 to 100 ng/ml.     

Analysis of anodic current transient measured on Pd electrode with fractal surface: Hydrogen diffusion coupled with interfacial charge transfer

Hydrogen transport through Pd electrode with fractally rough surface was investigated in 0.1 M NaOH solution by analysis of the anodic current transient. The Pd electrode surfaces were electrochemically modified to be rough by redox cycling in 1 M H₂SO₄ solution. From the triangulation analysis of the atomic force microscopy images, it was found that the modified electrode surfaces exhibited self-similar scaling properties with different fractal dimensions, depending upon the number of redox cycles. The anodic current transient measured on the surface-modified fractal electrode subjected to the hydrogen discharging potentials of 0.3-0.7 V reversible hydrogen electrode, (RHE) showed the non-generalised Cottrell behaviour, which resulted from the constraint of hydrogen diffusion mixed with interfacial charge transfer during hydrogen transport. Especially, it displayed an inflexion point at the time that corresponds to the temporal outer cut-off of fractality, i.e. the crossover time required for the fractal to flat transition. In addition, the temporal outer cut-off under the constraint of mixed control was observed to be shortened with increasing hydrogen discharging potential, which could be accounted for by the increased growth rate of diffusion layer in the electrode accompanying the facilitated charge transfer kinetics at the electrode/electrolyte interface.     

Effect of cell pressure on the electrochemical performance of all-solid-state lithium batteries with zero-excess Li metal anode

All-solid-state cells (ASSCs) typically operate at a specific pressure to ensure good contact between the solid electrolyte and the electrode-active materials. However, establishing the ideal cell pressure is challenging because of the various cell structures, the mechanical characteristics of solid electrolytes, and the extent to which the volume of the electrodes changes during cycling. In this study, we propose a specially designed cell assembly that adjusts to the changes in volume that occur during cycling while maintaining a constant cell pressure. The evaluations indicate that the spring in the cell assembly effectively reduces the stress incurred from the volume expansion that occurs in the electrode during charging (lithiation) and the volume contraction that occurs during discharging (delithiation) while maintaining the prescribed cell pressure. The capacity fading—as a function of the cycle number—decreases when operating ASSCs comprising a cell assembly that include a spring, compared with those that exclude a spring. Focused ion beam–scanning electron microscope reveals no cracks and delamination in the LiNi_0.8Co_0.1Mn_0.1O₃ (NCM811) composite cathode of the ASSCs, operated at 25 MPa, with a spring-equipped assembly. The Ag nanolayer that deposits on the Cu foil is an effective collector metal, forming a dense lithium plating layer on the Ag/Cu foil anode.     

Electrochemical lithiation and delithiation of LiMnPO4: Effect of cation substitution

The electrochemical lithiation-delithiation reaction was examined for LiMnPO₄ in which different cations were substituted for part of Mn. The X-ray diffraction analysis indicated that LiMnPO₄ is tolerant, to some extent, to substitution of Mg²⁺, Ca²⁺ and Zr⁴⁺. The substitution of Mg²⁺ and/or Zr⁴⁺ led to an increased reversible capacity and a reduced polarization, whereas Ca²⁺ substitution had a detrimental effect on the electrochemical properties. The potential transient analysis showed that LiMn_0.88Mg_0.1Zr_0.02PO₄ has higher lithium diffusivities than pure LiMnPO₄, indicating facilitated diffusion kinetics in the substituted material. Upon the first charge-discharge cycle, LiMn_0.88Mg_0.1Zr_0.02PO₄ suffered less irreversible capacity loss when compared with LiMnPO₄, and smaller amounts of electrolyte salt-based species were detected on the electrode surface of LiMn_0.88Mg_0.1Zr_0.02PO₄.     

Mission Analysis and Planning System for Korea Multipurpose Satellite-I

The Mission Analysis and Planning System (MAPS) has been developed for a low earth orbiting remote sensing satellite, Korea Multipurpose Satellite-I (KOMPSAT-I), to monitor and control the orbit and the attitude as well as to generate mission timelines and command plans. The MAPS has been designed using a top-down approach and modular programming method to ensure flexibility in modification and expansion of the system. Furthermore, a graphical user interface has been adopted to ensure user friendliness. Design, implementation, and testing of the KOMPSAT MAPS is discussed in this paper.     

Performance characteristic of a tubular carbon-based fuel cell short stack coupled with a dry carbon gasifier

A carbon gasified carbon-based fuel cell (CFC) short stack was fabricated and investigated for generating effective carbon fuel cell reactions. Anode-supported tubular CFC cells with a 45 cm² active electrode area were used to manufacture the CFC short stack, which was coupled with a dry gasifier induced by a reverse Boudouard reaction. Activated carbon (BET area 1800 m²/g) powder was mixed with K₂CO₃ powder (5 wt.%) and used to fill a dry gasifier as a solid carbon fuel, and pure CO₂ gas was supplied to the gasifier. The CO fuel generated by the reverse Boudouard reaction in the dry gasifier increased the performance of the CFC short stack. The tubular CFC short stack showed a maximum power of 29.4 W at 800 °C. It was operated under a range of operating conditions by changing the operating temperature, flow rate of the pure CO₂ and the thermal cycle operation. The results indicate that the fabricated tubular CFC is a promising power generation system candidate for many practical applications, such as residential power generation (RPG) and stationary power systems.     

Power source research at USC: Development of advanced electrocatalysts for polymer electrolyte membrane fuel cells

This paper provides an overview on the development of advanced fuel cell cathode catalysts at University of South Carolina (USC) with the emphasis on the stability of non-precious metal and Pt alloy catalysts. Nitrogen-modified carbon composite (NMCC) catalysts were developed for the oxygen reduction reaction (ORR) through the pyrolysis of cobalt (iron)-nitrogen chelate followed by the treatment combination of pyrolysis, acid leaching, and re-pyrolysis. A promising stability was observed for 1050 h fuel cell operation under current density of 200 mA cm⁻² as evidenced by a potential decay rate as low as 40 μV h⁻¹. The performance degradation mechanism of the NMCC-based fuel cell is discussed. Pt and PtPd hybrid catalysts are developed that use a NMCC, which is itself active for the ORR, instead of a conventional carbon black support. The stability test at 1 A cm⁻² indicated that the Pt/NMCC hybrid catalyst (new Pt-Co/C) is more stable than the conventional Pt-Co/C without the Co leaching out. The PEM fuel cell accelerated stress test (AST) for supports and catalysts demonstrated that their stability changes in the order: Pt₃Pd₁/NMCC hybrid catalyst > Pt/NMCC hybrid catalyst > conventional Pt/C catalyst. Moreover, the hybrid catalysts exhibit higher mass activity than the Pt/C catalysts.     

Cu- and Ni-doped Mn1.5Co1.5O4 spinel coatings on metallic interconnects for solid oxide fuel cells

An interconnect in solid oxide fuel cells electrically connects unit cells and separates fuel from oxidant in the adjoining cells. Metallic interconnects are usually coated with conductive oxides to improve their surface stability and to mitigate chromium poisoning of a cathode. In this study, Mn_1.5Co_1.5O₄ (MCO) spinel oxides doped with Cu and Ni are synthesized and applied as protective coatings on a metallic interconnect (Crofer 22 APU). Doping of Cu and Ni into MCO improves sintering characteristics as well as electrical conductivity and thermal expansion match with the Crofer interconnect. The dense layers of Cu- and Ni-doped MCOs are fabricated on the interconnects by a slurry coating process and subsequent heat-treatment. The coated interconnects exhibit area-specific resistances as low as 13.9–17.6 mΩ cm² at 800 °C. The Cu-doped MCO coating acts as an effective barrier to evaporation and migration of Cr-containing species from the interconnect, thereby reducing Cr poisoning of a cathode.