Eon Soo Lee

A Review on Non-PGM Cathode Catalysts for Polymer Electrolyte Membrane (PEM) Fuel Cell

In recent years, people attach high attention to the energy problem owing to the energy shortage of the world. Since the price of energy resources significantly increases, it is a necessary requirement to develop new alternative sources of energy to replace non-renewable energy resources. Polymer electrolyte membrane (PEM) fuel cell technology is one of the promising fields of clean and sustainable power, which is based on direct conversion of fuel into electricity. However, at the present moment PEM fuel cell is unable to be successful commercialization. The main factor is the high cost of materials in catalyst layer which is a core part of PEM fuel cell. In order to reduce the overall system cost, developing active, inexpensive non-platinum group metal (non-PGM) electrode catalysts to replace currently used Platinum (Pt)-based catalysts is a necessary and essential requirement. This paper reviews several important kinds of non-PGM electro-catalysts with different elements, such as nitrogen, transition metal, and metal organic frameworks (MOF). Among these catalysts, transition metal nitrogen-containing complexes supported on carbon materials (M-N/C) are considered the most potential oxidation reduction reaction (ORR) catalysts. The main synthetic methods are high temperature heat treating (800–1000°C). The mechanical and electrochemical properties of the final product will be analyzed by several characterization methods. For example, a RRDE test will be used to measure electron transfer number and ORR reactivity, which are the most important electrochemical properties of the new catalyst. And the morphology, particle size, crystal phase and specific surface area can be analyzed with SEM, TEM, XRD and BET methods. Although great improvement has been achieved in non-PGM catalyst area of research, there are still some challenges in both ORR activity and stability of non-PGM catalysts. Consequently, how to improve the ORR activity and stability are the major challenge of non-PGM catalyst research and development. Based on the results achieved in this area, our future research direction is also presented and discussed in this paper.Copyright

Simulation of Nano Polymer Chain Sensor in Electroosmotic Flow Using Dissipative Particle Dynamics (DPD) Method

In this paper, we simulate the inflation of fixed two ends polymer chain curvature as nano sensor in EOF which it provides a porous media for DPD (dissipative particles dynamics) solvent particles and inflation is resulted. Particles are driven by electroosmotic flow in nanochannel which is as an external force in DPD algorithm and part of particles should move through a non-charged polymer chain which they affect on curvature of polymer chain. Our results for simple nanochannel in EOF are validated with analytical results and we have developed our results when a fixed two ends polymer chain subject in nanochannel as nano sensor in both cases including simple and stenosis nanochannel. Amount of inflation (displacement) of fixed two ends polymer chain is related to electroosmotic forces and interaction between particles. Our aim is that a relation between effective parameters in electroosmotic flow such as electric field, zeta potential, kh parameters and amount of inflation in polymer chain curvature (interaction between particles) is provided for each test case. Based on our results, there is a linear relation between some parameters such as external electrical field, zeta potential and kh parameters (effect of Debye length and channel height) in low electrosmotic forces but non-linear behavior is observed for high electroosmotic forces especially for stenosis channel case. This study opens some new way toward designing proper nano EOF sensors to measure flow characteristics in EOF applications.Copyright

LBM Simulation of Electro-Osmotic Flow (EOF) in Nano/Micro Scales Porous Media With an Inclusive Parameters Study

In this paper, we present our results about simulation of 2D-EOF in Nano/Micro scales porous media using lattice Boltzmann method (LBM) in micro-channel for EOF. The high efficient numerical code use strongly high nonlinear Poisson Boltzmann equation to predicate behavior of EOF in complex geometry. The results are developed with precisely investigation of several effective parameters on permeability of EOF, such as geometry (channel height and number and location of charge), external electric field, thickness of Debye length (ionic concentration), and zeta potential. Our results are in excellent agreement with available analytical results. Our results show that for certain external electric field, zeta potential and porosity, there is an optimal Kh parameter (ionic concentration and channel height in this study) for velocity profiles. Based on the current study, homogenous zeta potential distribution on solid porous media, zeta potential and thickness of Debye length (Kh parameter) can dramatically affect on EOF permeability linearly or non-linearly, depend on amount of quantities. Thus, different arrangements are also considered. We show that prediction of EOF behavior in complex geometry with regarding role of effective parameters is completely possible for various applicable conditions.Copyright

Similar Region in Electroosmotic Flow Rate for Newtonian and Non-Newtonian Fluids Using Dissipative Particle Dynamics (DPD)

In this paper, analysis of electroosmotic flow in Newtonian and non Newtonian fluids in nanochannel with dissipative particle dynamics (DPD) method is presented and our results are validated with analytical solutions. Our aim is that which region or regions, based on the volumetric flow rates, in non-Newtonian fluids are similar with comparison to Newtonian ones in regards to various effective EOF parameters. For numerical simulation, the linearized Poisson Boltzmann for external force calculation is used and DPD method is applied for power law fluids to predict non-Newtonian fluids behavior in electroosmotic in various conditions such as different zeta potential, external electric fields, kh parameter (mainly Debye length and channel height), and flow behavior index. Based on the our results, for certain values of effective parameters, there are regions for volumetric flow rates which both Newtonian and non Newtonian electroosmotic flows have similar behavior while out of these regions, there are obviously significant differences and it is not possible to take Newtonian assumption for these regions. Based on our results validated with analytical solution, simplified assumption of taking non Newtonian fluid as Newtonians ones, in different EOF conditions in most cases, have a clearly inaccuracy and presented method can predict which EOF rates in both cases are correctly similar.Copyright