Experimental Investigation of the Influence of Pressure on the Performance of Polymer Electrolyte Water Electrolysis Cells
Conventional, mechanical compression of hydrogen to the above mentioned pressure levels is inefficient, noisy and many compression stages are required which cause high investment costs and intensive maintenance. In contrast, electrochemical compression in high pressure (HP) PEEC promises to be more efficient, silent and low maintenance. On the one hand theoretically higher pressure leads to higher thermodynamic voltages, while on the other hand it may decreases the transport losses due to smaller gaseous bubbles, especially at high current densities .
Experimental results of HP-PEEC up to several hundred bar are discussed, investigating the influence of HP on transport losses at high current densities. The evolution of the different overvoltages (kinetic, ohmic, mass transport), determined using high frequency resistance measurements and tafel extrapolation, is discussed as a function of gas pressure. In detail the influence of different porous titanium sinter current collector media on mass transport losses is discussed as function of temperature, pressure and current density. It is shown that there seems to be an optimum average pore diameter at about 10 µm (Fig. 1).
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