Sang C. Lee

Nitrogen functionalized graphite nanofibers/Ir nanoparticles for enhanced oxygen reduction reaction in polymer electrolyte fuel cells (PEFCs)

Nitrogen functionalization of graphite nanofibers (N-GNF) was performed using hexa methyl tetra amine (HMTA) as the nitrogen source and used as a support material for metal nanoparticle deposition. The successful incorporation of nitrogen was confirmed using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy analysis. Iridium (Ir) nanoparticles with a particle size of ∼2.2 nm were deposited onto N-GNF by a simple ethanol reduction method. The oxygen reduction reaction (ORR) activity of N-GNF and the ameliorating effect of ORR on Ir deposited N-GNF (Ir/N-GNF) were studied by various physicochemical and electrochemical methods. The enhancement of ORR activity for Ir/N-GNF was evidenced by high onset potentials and mass activities. The presence of nitrogen in the Ir/N-GNF catalyst facilitates quick desorption of the –OH species from the Ir surface and accelerates the electrochemical reaction of Ir particles which in turn enhances the ORR activity. The electrochemical stability of the Ir/N-GNF was investigated by repeated potential cycling up to 2500 cycles and was found to have excellent stability for ORR activity. The PEFC with Ir/N-GNF catalyst delivers a peak power density of 450 mW cm−2 at a load current density of 1577 mA cm−2, while the PEFC with Ir/GNF catalyst delivers a peak power density of only 259 mW cm−2 at a load current density of 1040 mA cm−2 under identical operation conditions.

A Review of the Application of CNTs in PEM Fuel Cells

Fuel cells are an important source of renewable energy technology and currently the subject of much research. Hydrogen gas, which is the main fuel source in fuel cells, is relatively easily available, and the exhaust does not consist of greenhouse gases, unlike fossil fuel-based power sources. Some of the challenges persisting in fuel cell technology are the cost of the fuel cell due to factors such as platinum catalyst loading and water management. This study reviews the use of carbon nanotubes (CNTs) in fuel cell applications. CNTs have a large number of superior properties, including electrical conductivity, thermal conductivity, mechanical strength, and ability to support catalysts by providing an increased surface area. Carbon nanotubes offer great promise for overcoming the problems of existing fuel cells. However, they still pose challenges of functionalization on components of the polymer electrolyte membrane fuel cell (PEMFC), namely the membrane electrode assembly (MEA), the gas diffusion layer (GDL), and the bipolar plates. This paper discusses various experimental techniques that have achieved success in this functionalization process. Application of CNTs in fuel cells is expected to improve fuel cell performance and efficiency and bring down the cost by reducing platinum (Pt) catalyst loading

Novel mesoporous microspheres of Al and Ni doped LMO spinels and their performance as cathodes in secondary lithium ion batteries

ABSTRACT A facile, scalable, and solution-based technique is used to fabricate Al and Ni-doped (LiAl0.1Mn1.9O4 and LiAl0.1Ni0.1Mn1.8O4) microspheres of lithium manganese oxide (LMO) spinels for use as reversible cathode materials for lithium ion batteries (LIBs). The spheres of the two samples exhibit different porosities. Cells with these LMO-based cathodes are then cycled between 4.5 V and 2 V to study their stabilities while simultaneously being subjected to the undesirable Jahn-Teller distortion that occurs around the ~3 V regime. The LiAl0.1Mn1.9O4 (LAMO) and the LiAl0.1Ni0.1Mn1.8O4 (LANMO) cells exhibit comparable open circuit voltages (OCV) of 2.94 V and 2.97 V, respectively. During cell cycling, the LAMO cell exhibits a maximum specific capacity of 122.51 mAh g−1 with a capacity fade of 65.35% after 75 cycles. The LiAl0.1Ni0.1Mn1.8O4 (LAMO) sample fares better and exhibits a maximum of 140.49 mAh g−1 and a capacity drop of 52.59%. Detailed structural studies indicate that Ni doping and the greater degree of porosity of the LANMO sample to be a stabilizing factor. This is further confirmed by cyclic voltammetry (CV) and AC impedance spectra analysis.

Bio-inspired robot platform powered by a commercial PEM fuel cell

Robots have come up as an emerging technology to assist humans in performing those repetitive and dangerous tasks which humans prefer not to do, or are unable to do due to size limitations and extreme environmental conditions. So the design of robots is required to be stringent to be able to operate at any environmental conditions. A wheeled robot is the one mostly associated in mobile robot operations. But a wheeled robot can travel only on smooth surface and not at irregular surface conditions. To overcome this, the robots mobile platform equipped with an efficient structure and function is required. Another issue with mobile robot is the power source which is generally battery. The disadvantage of battery is its low efficiency and low energy density. To override the above two issues, A competent robot platform suitable for irregular areas is designed and the conventional power source is replaced with a fuel cell to develop an efficient and environmental independent robot.