Medium Temperature – Polymer Electrolyte Membrane Fuel Cells (MT-PEMFCs) operate at temperatures between 80 °C and 120 °C. They show various advantages compared to traditional low temperature PEMFCs operating up to 80 °C: The management of liquid water is simplified, the electrode kinetics are enhanced and the tolerance to impurities contained in the reactant stream is increased [1–6]
. However, huge deficits in terms of cell performance and durability to date hinder the application of MT-PEMFCs in the field of hydrogen mobility 
. We present a novel manufacturing method called ‘direct membrane deposition’ 
in combination with TiO2
reinforcement which enables well performing MT-PEMFCs. The direct deposition of the reinforced membrane is realized by drop casting a dispersion of Nafion® and TiO2
nanoparticles onto anode and cathode gas diffusion electrodes. The fuel cell is assembled with the two membrane layers facing each other, completely substituting the commonly used membrane foil. A scheme of the membrane electrode assembly (MEA) fabricated for this work is depicted in Figure 1 a). MT-PEMFCs constructed this way allow stable fuel cell operation at 120 °C with a maximum power density of 2.0 W/cm2
; 0.5/0.5 L/min; 300/300 kPaabs.
, 90% RH). With increasing temperature from 80 °C to 120 °C, the membrane resistance of the TiO2
reinforced directly deposited membrane increases by only 10 % whereas the membrane resistance of a non-reinforced directly deposited membrane increases by 54 %. At 100 °C (120°C) the maximum power density of the fuel cell with directly deposited TiO2
reinforced membrane is 27 % (9 %) higher than the maximum power density of our reference system. The corresponding polarization curves are depicted in Figure 1 b). The reference fuel cell was manufactured with a Nafion® HP (DuPont) membrane, which, to our knowledge, is the thinnest commercially available reinforced membrane. As the main reason for the higher power densities compared to a state-of-the-art Nafion® HP membrane a lower membrane- and charge transfer resistance is found. In this work we show that TiO2
reinforcement has proven to effectively stabilize the membrane resistance of directly deposited Nafion® membranes at elevated fuel cell operation temperatures. Surprisingly, MT-PEMFCs constructed this way are able to outperform even state-of-the-art Nafion® HP membranes.
Figure 1: a) Illustration of the membrane electrode assembly (MEA) fabricated in this work. A thin TiO2 reinforced Nafion® layer is deposited directly on both anode and cathode gas diffusion electrodes. A thin subgasket prevents hydrogen and current crossover through the end faces of the active area. b) Shows a comparison of the polarization curves for a directly deposited membrane (DDM) to a commercial Nafion® HP (DuPont) membrane. For each membrane the current density characteristics power density is evaluated at 100°C (blue dashed curves) and 120°C (red curves). The operation conditions were: H2/O2; 0.5/0.5 L/min; 300/300 kPa, 90% RH.
This work was funded by the German Federal Ministry of Education BMBF within the project “Gecko” (03SF0454C).
 V. P. McConnell, Fuel Cells Bulletin 2009, 12.
 Q. Li, R. He, J. O. Jensen, N. J. Bjerrum, Chem. Mater. 2003, 15, 4896.
 J. Zhang, Z. Xie, J. Zhang, Y. Tang, C. Song, T. Navessin, Z. Shi, D. Song, H. Wang, D. P. Wilkinson, Z.-S. Liu, S. Holdcroft, J. Power Sources 2006, 160, 872.
 J.-R. Kim, J. S. Yi, T.-W. Song, J. Power Sources 2012, 220, 54.
 A. Chandan, M. Hattenberger, A. El-kharouf, S. Du, A. Dhir, V. Self, B. G. Pollet, A. Ingram, W. Bujalski, J. Power Sources 2013, 231, 264.
 S. Bose, T. Kuila, Nguyen, Thi Xuan Hien, N. H. Kim, K.-t. Lau, J. H. Lee, Progress in Polymer Science 2011, 36, 813.
 A. Stassi, I. Gatto, E. Passalacqua, V. Antonucci, A. S. Arico, L. Merlo, C. Oldani, E. Pagano, J. Power Sources 2011, 196, 8925.
 M. Klingele, M. Breitwieser, R. Zengerle, S. Thiele, J. Mater. Chem. A 2015.