Interfaces triphase

Two types of porous electrodes can be considered two- and three-phase systems, where the latter is the special case of a triphasic interface in fuel cells, where the gas, liquid, and solid coexist. In the former, the liquid reactant is dissolved in the electrolyte and transported to the active sites of the electrocatalyst. In each case, we can consider uniform, parallel, cylindrical, or conical pores that are topped at the bottom by the metal substrate and at the top by the electrolyte [19,20],... 

The design of the electrochemical reactor, in the case of a fuel cell, is not yet totally solved as classical heterogeneous chemical reactors do not meet the requirements of the triphasic interface anode and the cathode binary system. Some papers [1-3] have considered the problem at the cathode and at the anode independently. However, the electrocatalytic reactions on both the electrodes produce a single chemical reaction, which is the chemical outlet of the energy conversion process. 

The ideal 2D nano-reactors of the interfaces between immiscible fluids in stratified flows (Fig. 7b) have been used for chemical synthesis, triphase hydrogenation, and biological enzymatic degradation for extraction and separation and for kinetic smdies. 

Spalazzi JP, Doty SB, Moffat KL, Levine WN and Lu HH. Development of controlled matrix heterogeneity on a triphasic scaffold for orthopedic interface tissue engineering. Tissue Eng. 2006 12 3497-3508. 

Regen (1977) has extended these studies to include the interaction of water with a polystyrene matrix containing pendant poly(ethylene glycol monomethyl ether) groups. This type of polymer has been used in triphase catalysis (see Chapter 13). It was demonstrated that relatively fluid polar and nonpolar zones existed within the polymer and that, upon changes in solvent composition, either a contraction of the polar-nonpolar interface occurred, or the polarity and viscosity in the polar and nonpolar zones were changed. 

In a triphase catalytic system, reagents from two immiscible liquid phases are transferred to the interface of a solid where they react. The products formed at the interface are then returned to the liquid phases in which they are soluble. Typically, for a nucleophilic displacement reaction carried out under triphase conditions an... 

With the introduction of CNTs, it was possible to integrate CNT-based catalytic layers with a GDE. By modifying MWCNTs with PTFE, for example, a GDL is created that provides microstructured gas channels for efficient oxygen supply and provides a materials architecture with electric conductivity, mechanical stability, and water repellency. The resulting triphase interface is formed on the outside of the teflonized CNT particles. The aqueous electrolyte will primarily occupy the larger pore spaces, whereas the gas transport is ensured by the hydrophobic PTFE microchannels. 

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