Visualization of Liquid Water in a Metal Foam Flow-Field Based Polymer Electrolyte Fuel Cell Via Neutron Radiography

Abstract

Polymer electrolyte fuel cells (PEFCs) have shown significant advances in terms of performance, efficiency and durability for a wide range of applications. Flow-fields are crucial components that affect the water management and performance of PEFCs. The existence of gas channel and land configurations in the conventional flow-field designs render gas and water distribution highly non-uniform. Such issue can lead to a series of events detrimental to PEFC performance and longevity [1]. As an alternative, new type of flow-field such as metal foam has been introduced. In-depth understanding of water management in metal foam flow-field based PEFC is indispensable for the optimisation of performance and durability. Here, liquid water formation and transport across the 25 cm2 metal foam flow-field based PEFC is evaluated using neutron radiography. A nickel foam was put on cathode aluminium plate and a silicone gasket was then placed around the foam to seal in gases. A vertical single-channel serpentine was used for the anode aluminium flow-field, as shown in Fig. 1 (a). All experiments were conducted at the cold neutron radiography (CONRAD) beamline facility at Helmholtz-Zentrum Berlin (HZB). The setup for neutron imaging has been described in [2]. The result showed the enhancement of mass transport and cell performance in the metal foam flow-field compared to the conventional triple-serpentine design. Correlation of performance to neutron radiography reveals that the performance deviation in the mass transport region is likely due to flooding issues. The metal foam flow-field based PEFC exhibits less flooding and better uniformity in the local water distribution compared with that of serpentine flow-field design (Fig. 1 (b)). [1] Wu, Y., et al. "Effect of serpentine flow-field design on the water management of polymer electrolyte fuel cells: An in-operando neutron radiography study." Journal of Power Sources 399 (2018): 254-263. [2] Wu, Y., et al. "Effect of compression on the water management of polymer electrolyte fuel cells: An in-operando neutron radiography study." Journal of Power Sources 412 (2019): 597-605. Figure 1