Impact of Position and Platinum Loading of Recombination Interlayers in Proton Exchange Membranes on the Anodic Hydrogen Content in Water Electrolysis

Abstract

Hydrogen crossover through the membrane is a significant safety concern in proton exchange membrane water electrolyzers (PEMWEs). This issue is predominant at low loads, which contradicts the application of PEMWEs in conjunction with fluctuating renewable energy sources that require the electrolyzer to switch between low- and high-load operation. The risk of flammable or explosive oxygen-hydrogen mixtures on the anode side of the electrolyzer prevents the application of membranes as thin as in fuel cells, which results in relatively large Ohmic losses. A means to mitigate the accumulation of hydrogen in the oxygen compartment is the integration of platinum nanoparticles as a recombination catalyst interlayer within the membrane that catalyzes the recombination of hydrogen and oxygen to water. It was shown that such an interlayer effectively minimizes the hydrogen concentration on the anode side without reducing the cell performance.1 Thus, this technology can pave the way toward thinner membranes and more efficient electrolyzers.However, the interlayer should not increase the costs of the membrane electrode assembly by excessive Pt loading. Hence, we investigated the ideal position of this recombination interlayer within the membrane,2 and we performed a parameter study on the minimum required catalyst loading for an effective hydrogen-in-oxygen reduction.3 We find that the best position for the interlayer is close to the anode due to the lower oxygen permeability of the membrane. Also, a loading of 10 µg per cm² of platinum nanoparticles is sufficient to reduce the anodic hydrogen content from more than 2.5 vol.% (without interlayer) to approx. 0.5 vol.% when operating a PEMWE cell with a 110 µm thick membrane at 0.5 A/cm² and a differential pressure of 10 barc/1 bara. In summary, we are able to show that low platinum loadings within the membrane are sufficient to reduce the anodic hydrogen content in PEMWEs to safe values without impairing the electrochemical performance of the cell.References C. Klose, P. Trinke, T. Böhm, B. Bensmann, S. Vierrath, R. Hanke-Rauschenbach and S. Thiele, J. Electrochem. Soc., 165(16), F1271-F1277 (2018).A. Martin, D. Abbas, P. Trinke, T. Böhm, M. Bierling, B. Bensmann, S. Thiele and R. Hanke-Rauschenbach, J. Electrochem. Soc., 168(9), 94509 (2021).D. Abbas, A. Martin, P. Trinke, M. Bierling, B. Bensmann, S. Thiele, R. Hanke-Rauschenbach and T. Böhm, J. Electrochem. Soc., 169(12), 124514 (2022).