In past decades, researchers focus on developing series of alloy and core–shell electrocatalysts with high oxygen reduction reaction activity in order to alleviate the low Pt loading caused performance loss. The key to address the cost issue of polymer electrolyte membrane fuel cells (PEMFCs) lies on reducing Pt amount employed in cathode catalyst layers (CCLs). The model showed that the best membrane performance comes from a 100 ☌ operating temperature, with much better performance yielded from a higher pressure of 3 bar.
The model was trained on the experimental data and then used to predict the behaviour in the membrane region to understand how the fuel cell performs at varying temperatures and pressures. Nafion 211 is shown to have some interesting characteristics at elevated temperatures previously unreported, the first of which is that the highest performance reported is at 100 ☌ and 100% relative humidity. Modelling is used to investigate complex systems to gain further information that is challenging to obtain experimentally. However, current research excludes this due to issues with membrane durability. Increasing the fuel cell operating temperature could have many key benefits at the cell and system levels. This paper evaluates the performance of Nafion 211 at elevated temperatures up to 120 ☌ using an experimentally validated model. Polarization curve scan direction (also considering averaging process on multiple consecutive scans), anode Pt loading as low as 0.035 mg cm-2, as well as H2 and O2 flow rates above 300 scm 3 min-1 have negligible impact on the performance of PGM-free based MEAs. The results indicate that PGM-free catalyst loading and air flow rate on the cathode are impactful variables. The tests were done in a differential cell hardware using a commercial Fe-N-C catalyst at the cathode. Additionally, anodic Pt catalyst loading and cathodic PGM-free catalyst loading were investigated. In this work, we systematically investigated the effect on performance of some operational variables, such as polarization curve scan direction, and gas flow rates. However, the extensive number of variables involved in the electrode preparation as well as in the fuel cell testing, poses severe challenge to compare results obtained in different labs. While the activity and durability of PGM-free catalysts have been boosted, the PEFC performance relies also on the electrode structure at the membrane electrode assembly (MEA) level. Similarly, an electrospun cathode with a Pt loading of 0.055 mg/cm(2) produced a maximum power density of 906 mW/cm(2) at 80 degrees C and 3 atm pressure with 2000 sccm fully humidified air and 500 sccm H-2.Įxtensive research efforts have been made on platinum group metal (PGM)-free electrocatalysts for oxygen reduction reaction, with the aim of lowering the cost hurdle of acidic polymer electrolyte fuel cells (PEFCs). 400 mW/cm(2) for a decal MEA with cathode/anode Pt loadings of 0.104/0.40 mg/cm(2).
Thus, the maximum power density for H-2/air fuel cell operation at 80 degrees C, 1 atm (ambient) pressure, 125 sccm H-2, and 500 sccm air was 437 mW/cm(2) for a nanofiber cathode at 0.065 mg(Pt)/cm(2) vs. The mass activity (0.16 A/mg(Pt) at 0.9 V) and electrochemical surface area (similar to 41 m(2)/g) of nanofiber cathodes were very high and more power was generated from nanofiber electrode MEAs than from a conventional MEA with decal electrodes.
In all experiments, the nanofiber anode had a fixed Pt loading of 0.10 mg/cm(2). MEA performance was evaluated in a hydrogen/air fuel cell, where power output was correlated with cathode Pt loading (0.029-0.107 mg(Pt)/cm(2)) and changes in fuel cell temperature (60 degrees C and 80 degrees C), pressure (up to 3.0 atm), and feed gas flow rates. Membrane-electrode-assemblies (MEAs) were fabricated with electrospun nanofiber electrodes containing Johnson-Matthey (JM) HiSpec 4000 catalyst and a Nafion 212 membrane.