Investigation of Mass Transport Losses in Polymer Electrolyte Electrolysis Cells

Dynamically operable polymer electrolyte water electrolysis cells (PEEC) are also targeted at storing excess electric energy from renewable sources in hydrogen and oxygen in order to prevent curtailment [1].

In the energy storage application, efficiency of the processes is of particular concern not to waste precious renewable electricity. PEEC allow operation up to current densities around 5 A/cm² and the losses increase accordingly. Similar as in fuel cells, different processes contribute to the voltage losses with increasing current. While the contribution of the ohmic overvoltage is well characterized and can easily determined by measuring the high frequency resistance of the cell [2], the catalytic and transport losses are more rarely investigated.

For determining the mass transport losses, also the catalytic losses need to be characterized, which needs careful analysis in particular when pressure varies over a wide range. The dependence of the transport losses is determined as function of the structures employed as current collectors, i.e. possible two phase phenomena in the porous structures as well as for different operating conditions with respect to pressure and temperature. The results show that over a wide range of current densities a quite significant part of the voltage losses can to be attributed to mass transport.

[1] C.J. Barnhart, et al., Energy Environ. Sci., 6, 2804-2810 (2013).

[2] C. Rozain, P. Millet, Electrochim. Acta, 131, 160-167 (2014)