Acid holder matrix

The phosphoric acid is required to be Immobilized in between the two electrodes. For this, an acid holder matrix is created on one or both the electrodes. The matrix is a sponge type material that holds the syrupy... 

A basic PAFC stack configuration is given in Fig. 13. The anode-acid holder matrix-cathode sandwich is held between two bipolar plates and this array is repeated to the end. At each end there is an one-side grooved plate—one with anode groove and the other end with cathode groove. Each of these plates have through holes, when assembled act as reactant gas flow headers (inlet and outlet). The inlet header of one gas has an opening in one side of each bipolar plate, and similarly the outlet header of the same gas collects excess unreacted reactants/products from the same side of the bipolar plates. The inlet and outlet headers of the other gas similarly feed and collect gas from the other side of the bipolar plates. 

Hydrogen electrode (anode) I- Acid holder matrix... 

The latest generation of PAFC units employ mixture of various technologies. Ribbed electrode design as well as Toray developed thin diffusion layer with separate acid reservoirs are employed depending upon the design, capacity and the availability of the fuel cell materials. For fully hydrophobised electrode substrate, one has to provide acid links from the reservoirs located in bipolar plates to the acid holder matrix. This is possible, by making part of the substrate hydrophilic, and is achieved by filling carbon or SiC particles inside the substrate to allow acid transport to the matrix by capillary action (DeCasperis et al., 1981, Schroll and Hartford, 1974). 

This desorption ionisation technique leads to weak fragmentation. The analyte is incorporated into a solid organic matrix (such as hydroxybenzoic acid) and the mixture is placed on a sample holder that is irradiated with UV laser pulses (e.g. N2 laser, A = 337 nm, pulse width = 5 ns). The laser energy is absorbed by the matrix and transferred to the analyte, which becomes desorbed and ionised (Fig. 16.18c). Although MALDI is considered to be a soft ionisation technique, a substantial amount of energy is involved. Because the technique involves pulsed ionisation, it is well suited for time-of-flight mass analysis of biomolecules. The analysis of small molecules (M < 500 Da) is limited because the matrix decomposes upon absorption of the laser radiation. However, solid supports such as silicone can be used as the matrix to overcome this disadvantage. 

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