Garbe, SteffenFutter, JonasAgarwal, AyushTarik, MohamedMularczyk, Adrian A.Schmidt, Thomas J.Gubler, Lorenz2021-05-222021-05-222021-05-222021-04-0110.1149/1945-7111/abf4aehttps://infoscience.epfl.ch/handle/20.500.14299/178248WOS:000640598500001The cost of polymer electrolyte water electrolysis (PEWE) is dominated by the price of electricity used to power the water splitting reaction. We present a liquid water fed polymer electrolyte water electrolyzer cell operated at a cell temperature of 100 degrees C in comparison to a cell operated at state-of-the-art operation temperature of 60 degrees C over a 300 h constant current period. The hydrogen conversion efficiency increases by up to 5% at elevated temperature and makes green hydrogen cheaper. However, temperature is a stress factor that accelerates degradation causes in the cell. The PEWE cell operated at a cell temperature of 100 degrees C shows a 5 times increased cell voltage loss rate compared to the PEWE cell at 60 degrees C. The initial performance gain was found to be consumed after a projected operation time of 3,500 h. Elevated temperature operation is only viable if a voltage loss rate of less than 5.8 mu V h(-1) can be attained. The major degradation phenomena that impact performance loss at 100 degrees C are ohmic (49%) and anode kinetic losses (45%). Damage to components was identified by post-test electron-microscopic analysis of the catalyst coated membrane and measurement of cation content in the drag water. The chemical decomposition of the ionomer increases by a factor of 10 at 100 degrees C vs 60 degrees C. Failure by short circuit formation was estimated to be a failure mode after a projected lifetime 3,700 h. At elevated temperature and differential pressure operation hydrogen gas cross-over is limiting since a content of 4% hydrogen in oxygen represents the lower explosion limit.ElectrochemistryMaterials Science, Coatings & FilmsElectrochemistryMaterials Scienceenergy storagewater electrolysisproton exchange membrane water electrolysispem water electrolysisdegradationelevated temperaturetext::journal::journal article::research article