The Hydro-electro-thermal Performance of Air-cooled, Open-cathode Polymer Electrolyte Fuel Cells: Combined Localised Current Density, Temperature and Water Mapping

Abstract

In situ diagnostic techniques provide a means of understanding the internal workings of fuel cells so that improved designs and operating regimes can be identified. Here, a novel metrology approach is reported that combines current and temperature mapping with water visualisation using neutron radiography.The approach enables a hydro-electro-thermal performance map to be generated that is applied to an air-cooled, open-cathode polymer electrolyte fuel cell. This type of fuel cell exhibits a particularly interesting coupled relationship between water, current and heat, as the air supply has the due role of cooling the stack as well as providing the cathode reactant feed via a single source. It is found that water predominantly accumulates under the cooling channels (thickness of 70-100 µm under the cooling channels and 5-25 µm in the active channels at 0.5 A cm KeywordsAir-cooled open-cathode polymer electrolyte fuel cell; water mapping; neutron imaging; temperature mapping; current mapping.

Nitrogen Blanketing and Hydrogen Starvation in Dead-Ended-Anode Polymer Electrolyte Fuel Cells Revealed by Hydro-Electro-Thermal Analysis

“…In air-cooled, open-cathode systems the temperature depends on the voltage and current density [67,78], air cooling flow rate [73,76], and heat transfer characteristics of the stack. In practice, the temperature management is normally performed using a single-point thermocouple inserted in the centre of the cell [18,29,75], or for development work using multiple microthermocouple measurements at various locations in the fuel cell [15,79,80].The authors have previously studied dead-ended operation, on a cell with dry fuel and air, using techniques such as mass spectrometry (revealing nitrogen 6 accumulation), thermal imaging and electrochemical impedance spectroscopy [29], as well as combined current and temperature mapping, revealing large gradients between the fuel inlet and exhaust [33].Here, we present the results obtained by applying the recently developed hydroelectro-thermal analysis [57] technique to an air-cooled, open-cathode fuel cell operated in dead-ended anode mode, to capture dynamic operation, combining current and temperature mapping with water mapping during dead-ended operation. …”

Effect of gas diffusion layer properties on water distribution across air-cooled, open-cathode polymer electrolyte fuel cells: A combined ex-situ X-ray tomography and in-operando neutron imaging study

“…Using neutron radiography on similar cells, previous imaging work in the throughplane direction showed that the area under the cathode cooling channel lands has the greatest concentration of water [38]. However, as imaging was performed in the through-plane direction, no information was available regarding the distribution of water within the layers of the MEA.…”

“…In the first case, it is possible to differentiate between the water content in the cathode and the anode GDL [29][30][31][32][33][34][35][36]. In the second case, it enables investigations of the effect of different designs, components, and operating conditions on the water distribution across the lateral extent of the cell [37][38][39][40][41][42][43][44][45][46][47]. Neutron imaging has been combined with other modelling and experimental techniques, such as current mapping [48], computational fluid dynamics (CFD) model validation [34,49,50], optical imaging [51], neutron scattering [52] and localised electrochemical impedance spectroscopy (EIS) [53].…”

“…Neutron imaging has been combined with other modelling and experimental techniques, such as current mapping [48], computational fluid dynamics (CFD) model validation [34,49,50], optical imaging [51], neutron scattering [52] and localised electrochemical impedance spectroscopy (EIS) [53]. The authors have recently combined neutron imaging with current and temperature mapping in a single device [37,38], linking water formation / evaporation with current density and temperature under steady state and transient conditions.…”

“…The comparison between both stacks has been performed in the region of the polarisation where a fuel cell will typically be operated and substantial water cell's GDLs due to high temperatures has been shown to occur using combined electro-hydro-thermal analysis [38]. At 0.5 A cm -2 , the anode of Stack-A appears relatively dry (Figure 8 b)) and the lateral diffusion of water under the CC land to the AC region, with a drop of water thickness from 1200 m to 400 m, can be assumed to be sufficient to remove most of the water from the cathode (Figure 7 a, Figure 8).…”