Laminar membraneless

Membraneless Opportunities with Laminar 4472 as Electrochemical Capacitors ... 

One way to ease any difficulties that may arise in fabricating a membrane, especially in design configurations that are not planar, is to go membraneless. Recent reports take advantage of the laminar flow innate to microfluidic reactors ° to develop membraneless fuel cells. The potential of the fuel cell is established at the boundary between parallel (channel) flows of the two fluids customarily compartmentalized in the fuel cell as fuel (anolyte) and oxidant (catholyte). Adapting prior redox fuel cell chemistry using a catholyte of V /V and an anolyte of Ferrigno et al. obtained 35 mA cmr at... 

An application of microfluidic reactors is the development of a membraneless fuel cell. Two streams, one containing a fuel such as methanol, the other an oxygen-saturated acid or alkaline stream, are merged without mixing. The laminar flow pattern in the narrow channel helps to maintain separate streams without the use of membrane separators. Opposite walls function as the electrodes and are doped with catalyst. Ion exchange, protons for the add system, takes place through the liquid-liquid interface. This is an example of a solid-liquid-liquid-solid multiphase reactor. ... 

Micro fuel cell designs without polymeric membranes can overcome some PEM-related issues such as fuel crossover, anode dry-out or cathode flooding. In these membraneless laminar flow-based fuel cells (LF-EC) two or more liquid streams merge into a single microfluidic channel. The stream flows over the anode and the cathode electrodes placed on opposing side walls within the channel. The reaction of fuel and oxidant takes place at the electrodes while the two liquid streams and their liquid-liquid interface provide the necessary ionic transport [122,123]. 

Finally, it is worth mentioning the microfluidic fuel cells concept [103] introduced by Whitesides in 2002 [104], based in a membraneless fuel cell design which exploit the laminar flowl that occurs in liquids flowing at low Reynolds number to eliminate convective mixing of fuels. Using this concept on-chip, membraneless, air-breathing monolithic pDAFC has been constmcted by Osaka and coworkers [105, 106] which operate with methanol, ethanol and 2-propanol solution containing sulphuric acid or phosphate buffer. The cell consists of two cathodes at the top of the channel, and the hquid fuel is supphed by capillary force to the anode formed on the bottom of the channel, as indicated in Fig. 1.12a, b. 

Ferrigno R, Stroock AD, Clark TD, Mayer M, Whitesides GM (2002) Membraneless vanadium redox fuel cell using laminar flow. J Am Chem Soc 124 12930-12931... 

Laminar flow-based fuel cells Membraneless fuel cells Microfluidic biofuel cells... 

Choban ER, Spendelow JS, Gancs L, Wieckowski A, Kenis PJA (2005) Membraneless laminar flow-based micro fuel cells operating in alkaline, acidic, and acidic/alkaline media. Electrochim Acta 50(27) 5390-5398... 

Mousavi Shaegh, S.A., Nguyen, N.-T., and Chan, S.H. (2011) A review on membraneless laminar flow-based fuel cells. Int.J. Hydrogen Energy, 36 (9), 5675-5694. 

Microfluidics is a relatively new branch of contemporary physics. It deals with fluid flow and transport phenomena in microstructures with at least one characteristic dimension in the range 1 to 1000 J,m. A microfluidic fuel cell (pFl-FC) (also called a membraneless fuel cell or laminar flow fuel cell) is a type of fuel cell in which all essential functions (i.e., reactant delivery, current-producing electrochemical reaction, and product removal) are conflned to a microfluidic channel. 

Figure 18.10 Schanatic of the membraneless laminar flow-based fuel cell. Regions of fuel-oxidant depletion as well as regions of diffusional fuel-oxidant crossover are indicated (not drawn to scale). (From Choban, 2004, with permission from Elsevier.)...

Microfluidic fuel cells, also known as membraneless fuel cells or laminar flow-based fuel cells, represent an emerging fuel cell technology capable of integration and operation within the framework of a microfluidic chip. In microfluidic fuel cells, all functions and components related to reactant delivery, reaction sites, and electrode structures are confined to a single microfluidic channel. Microfluidic fuel cells predominantly operate using co-laminar flow of fuel and oxidant electrolytes without a physical barrier, such as a membrane, to separate the two half-cells. 

Recently, membraneless laminar flow-based fuel cells are being explored and beginning to emerge. They are primarily aimed at avoiding ionomer membranes, which have disadvantages, most notably their change in size with humidification and their incompatibility with microtechnology. 

In this chapter, the fundamentals of the membraneless laminar flow-based fuel cells (LLFCs) operation are first explained. Then, design and exploited fabrication technologies of membraneless LFFCs and the effect of flow architectures of electrodes and their arrangements on cell performance are discussed. Subsequently, reader can find more details about the proposed fuels, oxidants, and electrolytes for membraneless LLFCs. Finally, some discussions on material constraints and selections are provided. 

Jayashree, R.S., Yoon, S.K., Brushett, F.R., Lopez-Montesinos, P.O., Natarajan, D., Markoski, L.J., and Kenis, P.J.A. (2010) On the performance of membraneless laminar flow-based fuel cells. Journal of Power Sources, 195 (11), 3569-3578. 

M.H. Ghang, F. Chen and N.S. Fang, Analysis of membraneless fuel cell using laminar flow in a Y-shap>ed microchannel, /. Power Sources 159, 2006,810-816. 

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