PEM fuel cell with lower platinum content
An international research group has designed a proton exchange membrane (PEM) fuel cell based on a hybrid electrocatalyst with lower platinum content. They claim it has remarkable stability and lower performance losses than other types of hybrid electrocatalysts.
They fabricated the oxygen reduction reaction (ORR) catalyst with platinum and iron (Pt–Fe) alloy nanoparticles on highly dispersed Pt and Fe single atoms in nitrogen-doped carbon support. This resulted in an ultra-low Pt loading of around 1.7wt%.
“However, as the Pt loading decreases, the oxygen transfer resistance increases because of the limited accessible active sites, which results in a lower durability,” the scientists warned. “Thus, the ambition to develop low-Pt-loading cathodes poses great challenges in the areas of Pt utilization and the intrinsic durability of Pt-based electrocatalysts.”
By scanning transmission electron microscope (STEM) images, the researchers found that the small nanoparticles used have an ordered structure, which is shown by the characteristically alternating bright and dim lattice. They said it also indicates the high order degree of the nanoparticles themselves. In addition, they used electron energy loss spectroscopy (EELS), which demonstrated the co-existence of abundant Pt and Fe single atoms and Pt–Fe nanoparticles in the hybrid material.
The academics measured the performance of the fuel cell in a hydrogen peroxide (H2/O2) environment and it exhibited a power density of 1.08 W cm–2 at 2.0 A cm–2, which they said is just a bit lower than that of a reference fuel cell with higher Pt loading. They also tested the device via accelerated durability testing under repeated square-wave cycles and it was able to retain 97% of its activity after 100,000 cycles, with no noticeable current drop at 0.6 V for over 200 hours.
“The enhanced durability of the hybrid electrocatalyst may result from a reduced H2O2 formation and consequent alleviation of the membrane and ionomer degradation,” they said.
They described their findings in “Atomically dispersed Pt and Fe sites and Pt–Fe nanoparticles for durable proton exchange membrane fuel cells,” published in Nature Catalysis. The research group includes scientists from the US Department of Energy Argonne National Laboratory, the Hong Kong University of Science and Technology, and the Southern University of Science and Technology in China.
“Our results highlight the importance of the synergistic effects among different active sites in hybrid electrocatalysts and provide an alternative way to design more active and durable low-Pt-group metal electrocatalysts for fuel cells and other electrochemical devices,” they concluded.
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[…] Argonne National Laboratory researchers have identified a fundamental source of instability in nickel-manganese-cobalt oxide (NMC) cathodes: the domain boundaries that are present in single-crystalline cathode particles. They have also developed a method to produce boundary-free single crystals, which could pave the way to longer-lasting, safer batteries. “We now have guidelines that battery manufacturers can use to prepare cathode material that is boundary free and works at high voltage,” said Khalil Amine, an Argonne distinguished fellow. The team looked at cathodes made from both coated polycrystals and single crystals and subjected them to extensive analysis. It turned out that what they had believed were single crystals, as evidenced by electron and X-ray diffraction microscopy, actually had boundaries inside. Their calculations at the atomic scale also showed how boundaries lead to oxygen release at high voltage and therefore performance decline. They described their findings in “Origin and regulation of oxygen redox instability in high-voltage battery cathodes,” which was recently published in Nature. […]
[…] Argonne National Laboratory researchers have identified a simple way to obtain instability in nickel-manganese-cobalt oxide (NMC) cathodes: the domain boundaries which are within single-crystalline cathode particles. They will have also developed a strategy to produce boundary-free single crystals, that could pave the best way to longer-lasting, safer batteries. We’ve guidelines that battery manufacturers may use to get ready cathode material that’s boundary free and works at high voltage, said Khalil Amine, an Argonne distinguished fellow. The team viewed cathodes created from both coated polycrystals and single crystals and subjected them to extensive analysis. It proved that what that they had believed were single crystals, as evidenced by electron and X-ray diffraction microscopy, actually had boundaries inside. Their calculations at the atomic scale also showed how boundaries result in oxygen release at high voltage and for that reason performance decline. They described their findings in Origin and regulation of oxygen redox instability in high-voltage battery cathodes, that was recently published in Nature. […]
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[…] A Chinese-US research group has designed a proton exchange membrane fuel cell with a hybrid electrocatalyst. The scientists said the device shows remarkable stability and low performance losses…Read More […]
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