Proton exchange membrane design

Zhang, L., Ma, C. and Mukerjee, S. 2003. Oxygen permeation studies on alternative proton exchange membranes designed for elevated temperature operation. Electrochimica Acta 48 1845-1859. 

The authors developed a multi-layered microreactor system with a methanol reforma- to supply hydrogen for a small proton exchange membrane fiiel cell (PEMFC) to be used as a power source for portable electronic devices [6]. The microreactor consists of four units (a methanol reformer with catalytic combustor, a carbon monoxide remover, and two vaporizers), and was designed using thermal simulations to establish the rppropriate temperature distribution for each reaction, as shown in Fig. 3. 

Figure 4. Schematic design of a proton exchange membrane fuel.

Significant (and even spectacular) results were contributed by the group of Norskov to the field of electrocatalysis [102-105]. Theoretical calculations led to the design of novel nanoparticulate anode catalysts for proton exchange membrane fuel cells (PEMFC) which are composed of trimetallic systems where which PtRu is alloyed with a third, non-noble metal such as Co, Ni, or W. Remarkably, the activity trends observed experimentally when using Pt-, PtRu-, PtRuNi-, and PtRuCo electrocatalysts corresponded exactly with the theoretical predictions (cf. Figure 5(a) and (b)) [102]. 

Obviously, in practical situations one can hardly imagine a vacuum pump installed onboard of a fuel cell-powered vehicle. Even if so, the membrane of a Proton Exchange Membrane Fuel Cell (PEMFC) will be soon contaminated by the oil vapors released from the pump (dry pumps are possible but this would enormously complicate the entire design). 

The use of chlorine in a fuel cell system for space power applications has been suggested [100]. The CI2/H2 system is based on a proton-exchange membrane fuel cell design and is shown to give superior power and energy density when compared to conventional systems. 

Other metals, the performances of which as cathodes in the electroreduction of C02 have already been described in detail, were suggested for the development stage. Thus, Delacourt et al. [87] proposed an electrochemical cell, the design of which was taken from proton exchange membrane fuel cell (PEMFC) technology,... 

In the proton-emitting membrane or proton electrolyte membrane (PEM) design, the membrane electrode assembly consists of the anode and cathode, which are provided with a very thin layer of catalyst, bonded to either side of the proton exchange membrane. With the help of the catalyst, the H2 at the anode splits into a proton and an electron, while Oz enters at the cathode. On the inside of the porous anode is a thin platinum catalyst layer. When H2 reaches this layer, it separates into protons (H2 ions) and electrons. One of the reasons why the cost of fuel cells is still high is because the cost of the platinum catalyst is rising. One ounce of platinum cost 361 in 1999 and increased to 1,521 in 2007. 

Figure 2.55. Illustration of the operation of proton exchange membrane (PEM) fuel cell. In this design, the electrolyte facilitates the transfer of protons across its membrane.

Tatapudi and Fenton [69] explored the synthesis of ozone in a proton exchange membrane (PEM) electrochemical flow reactor as part of an overall scheme to study the paired synthesis of ozone and hydrogen peroxide in the same PEM reactor. A mixture of commercially available lead dioxide powder and Teflon , deposited on a Nafion 117 membrane, was used as the anode. Current efficiencies ranged from 2.5% at an applied potential of 3.0 V to 5.5% at 4.0 V. The low current efficiencies were attributed to inefficient reactor design. A decrease in ozone concentrations, observed at higher applied potentials (> 4.0 V) was attributed to the disintegration of lead dioxide at high anodic potentials. 

Figure 3.33. Schematic picture of a proton exchange membrane fuel cell. Modelling of reactions at the gas diffusion layer/catalyst/membrane interfaces A and B is discussed in section 3.5.2. Details of design are discussed in the following subsections.

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