Elevated Temperature Proton Exchange Membrane Water Electrolysis for Reduced Cost of Green Hydrogen Production
Authors: Garbe Steffen , Schmidt Thomas J. , Gubler Lorenz 
Published: December 2020

Proton exchange membrane water electrolysis (PEMWE) is one of the most promising technologies for the production of green hydrogen through renewable energy sources [1]. A major obstacle of the technology to enter a large scale market is the high hydrogen production cost in comparison to traditional steam methane reforming (SMR). Recently, it has been shown that the capital expenditure (CAPEX) of PEMWE could be significantly reduced by application of new cell materials [2]. In order to further reduce the cost of green hydrogen it is necessary to reduce the operational expenditure (OPEX). On the one hand the OPEX is strongly driven by the electricity cost, on the other hand it can be reduced by increasing the efficiency of PEMWE [3].
One possibility to do so it to increase the operating temperature. This makes water electrolysis thermodynamically more efficient but also reduces the cell’s loss contributions. Additionally, the usage of thin membranes would lower ohmic overpotentials. Industrial electrolysers are currently operated at around 60°C and use thick membranes of about 200µm. The more demanding conditions of elevated temperature operation and the use of thin membranes are a challenge for the chemical and mechanical stability of the electrodes and the membrane [4]. Moreover, they imply a major safety concern due to increase of hydrogen crossover. Anticipated materials are required to master the more challenging operation mode.
In this study, we present a self-built test bench that allows to operate a PEMWE single cell of 25cm2 at temperatures of up to 120°C and use thin membranes of 60µm. By performing hydrogen permeation measurements, we are able to determine Faradic efficiency and the safety limits of PEMWE. Higher operating temperatures are not possible due to the safety limit of 2% hydrogen in oxygen in the anode compartment. A detailed cell loss analysis helps to understand to which extent the overpotential contributions can be reduced. Further, we show that with the advanced conditions the PEMWE efficiency increases by up to 14% at 3Acm-2 or an increase of the current density by 200% at an efficiency of 75% is possible (Figure 1a). The decrease in overpotential allows to significantly lower the electricity costs or to increase the production rate of hydrogen (Figure 1b).
[1] U. Babic, M. Suermann, F.N. Büchi, L. Gubler, T.J. Schmidt, Critical Review—Identifying Critical Gaps for Polymer Electrolyte Water Electrolysis Development, Journal of The Electrochemical Society, 164 (2017) F387-F399.
[2] K. Ayers, N. Danilovic, R. Ouimet, M. Carmo, B. Pivovar, M. Bornstein, Perspectives on low-temperature electrolysis and potential for renewable hydrogen at scale, Annual Review of Chemical and Biomolecular Engineering, 10 (2019) 219-239.
[3] J. Proost, State-of-the art CAPEX data for water electrolysers, and their impact on renewable hydrogen price settings, International Journal of Hydrogen Energy, 44 (2019) 4406-4413.
[4] C. Mittelsteadt, J. Willey, R. Stone, J. Riffle, J. Rowlett, A. Daryaei, J. McGrath, dings, US Department of Energy, Arlington, VA (USA), June 8-12, 2015

Figure 1