Water management in novel direct membrane deposition fuel cells under low humidification

Abstract

Direct membrane depositionNeutron radiography Water management Back diffusion a b s t r a c t Polymer electrolyte membrane fuel cells (PEMFCs) fabricated by direct membrane deposition (DMD) were shown to work even at dry conditions without significant deterioration of the membrane resistance. Here, in situ neutron radiography is used to investigate the water management in those fuel cells to uncover the phenomena that lead to the robust operation under low humidification. A constant level of humidification within the membrane electrode assembly (MEA) of a DMD fuel cell is observed even under dry anode operation and 15% relative humidity on the cathode side. This proves a pronounced back diffusion of generated water from the cathode side to the anode side through the thin deposited membrane layer. Over the entire range of polarization curves a very high similarity of the water evolution in anode and cathode flow fields is found in spite of different humidification levels. It is shown that the power density of directly deposited membranes in contrast to a 50 mm thick N-112 membrane is only marginally affected by dry operation conditions. Water profiles in through-plane direction of the MEA reveal that the water content in the DMD fuel cell remains steady even at high current densities. This is in contrast to the N-112 reference fuel cell which shows a strong increase in membrane resistance and a reduced MEA water content with raising current densities. Thus this new MEA fabrication technique has a promising perspective, since dry operation conditions are highly requested in order to reduce fuel cell system costs.

Dynamic acoustic emission analysis of polymer electrolyte membrane fuel cells

“…52 HFR is an index for the level of water uptake by a membrane and its associated conductivity. 49 The HFR initially decreases from ∼270 Ω cm 2 at 0.85 V to ∼150 Ω cm 2 at 0.55 V due to an increase in the hydration with increasing current. Later, HFR increases from ∼150 Ω cm 2 at 0.55 V to ∼175 Ω cm 2 at 0.3 V as a result of membrane dehydration due to increased temperatures at higher currents, which is a known trend from our previous work.…”

Humidification strategy for polymer electrolyte membrane fuel cells – A review

“…For example, Kong et al [65,66] enhanced the self-humidification by adopting double gas diffusion backing layers. Recently, Breitwieser et al [67] fabricated a PEMFC with direct membrane deposition [68] which facilitates the back diffusion from the cathode to the anode. The neutron radiography test was carried out and it is shown that the humidification level of the MEA stay constant even with dry anode and low cathode RH (15%).…”

Cerium Oxide Decorated Polymer Nanofibers as Effective Membrane Reinforcement for Durable, High‐Performance Fuel Cells

“…This is also in agreement with previous work, where significantly reduced values of R LF-HF were found for DMD fuel cells with a pure Nafion membrane, [31,44] in particular at high current densities. [33,46] Comparable improvements were reported for patterned membranes enhancing the catalyst layer/PEM interaction. [33,46] Comparable improvements were reported for patterned membranes enhancing the catalyst layer/PEM interaction.…”