Metal Foam - Fuel Cell Cold Start Performance Enhancement

Commercialized metal foamsare currently a good potential alternative to conventional runners for fuel cells due to their porous microstructure, high porosity, and good mechaNical strength.
First, the polarization performance of the battery under normal working conditions at room temperature was analyzed. Considering that the cathode is the main electrode that restricts the battery's performance, conventional parallel flow paths are used for the anode of both single cells, and conventional parallel flow paths are used for the cathode with a new nickel-metal Foam flow field, respectively.
To more distinctly reflect the flow differences and performance differences in the two flow fields, the study used a slender cell flow field with a size of 1.5 cm × 20 cm (the gases all flowed along the long side), which somewhat lost the original cell performance, and therefore, the cell polarization performance was not high. In addition, the same MEA (Nafion-112) was used for both cells in the test. Due to the higher curvature of the tiny flow channel in the foam metal flow field, the pressure drop at both ends is higher compared to the simple long straight flow channel in the conventional flow field, which enhances the gas supply to the cathode, the operating pressure, and the rate of electrochemical reaction, and at the same time, it needs to consume more pressurized gas engine power to a certain degree and increases the pumping loss. The maximum power density is higher for cells with metal foam flow fields, while at low currents, the power density is slightly lower than that of conventional flow field cells. Overall, the advantages of using a metal foam flow field are still significant. In the long run, due to the more uniform gas and liquid water flow in the foam metal flow field, a shorter flow field can be used in practical applications, or the use of cathode and anode vertical cross-supply (anode gas flows along the long side of the traditional flow channel, cathode gas flows along the short side of the foam flow field), which further reduces the pumping loss caused by the cathode inlet and outlet pressure drop, and thus is expected to realize the enhancement of the battery performance, and even maintain a comparable or even higher power density than the traditional flow channel, which can be achieved in the long run. Therefore, it is expected to realize the enhancement of cell performance while maintaining the pumping loss comparable to or even lower than that of the traditional flow channel.
On the other hand, to address the concern of sub-zero starting conditions, we comprehensively compare the dynamic starting performance of fuel cells with foam metal flow field and conventional parallel flow channel at the cathode under constant current and constant voltage modes, respectively.
On the other hand, for the popular sub-zero starting condition, we comprehensively compare the dynamic starting performance of fuel cells with foam metal flow field and conventional parallel flow channel at the cathode under constant current and constant voltage modes, respectively.
The foam-metal flow field shows excellent advantages, with stable cell performance during startup and successful startup, while on the contrary, the conventional parallel-flow channel cell, with lower and unstable cell output voltage during operation, improves the heat production rate and temperature rise rate to a certain extent, but due to the fewer flow channels, the possibility of icing and clogging increases linearly (depending on the number of flow channels), which leads to its fluctuating cell output performance However, the likelihood of ice clogging increases linearly (depending on the number of flow channels), resulting in a fluctuating cell output performance and an increased likelihood of start-up failure.
In summary, the excellent porous structure of the fuel cell with foam metal flow field has significant advantages over the cell with a traditional “trench-ridge” flow channel under both room temperature operation and sub-zero dynamic startup conditions.
The maximum power density and ultimate current density of the Battery at room temperature are increased by about 25%;
Under sub-zero starting conditions, the performance of batteries with foam metal flow field is smoother during starting, and the low-temperature self-starting ability is greatly improved.
In addition, the use of more optimized treatments for foam metal materials, such as gold plating to enhance conductivity, more appropriate hydrophobicity and corrosion resistance treatments, and the use of foam materials with more optimized pore sizes, porosity, and compression ratios, is expected to further strengthen the operational performance of the fuel cell and enhance the durability of the cold-start cycle.