Brown researchers develop new sturdy catalyst for key gas cell response; hard-magnet L10-CoPt nanoparticles
One issue holding again the widespread use of eco-friendly hydrogen gas cells in vehicles, vans and different autos is the price of the platinum catalysts that make the cells work. One method to utilizing much less valuable platinum is to mix it with different cheaper metals, however these alloy catalysts are inclined to degrade rapidly in gas cell circumstances.
Now, researchers from Brown College have developed a brand new alloy catalyst that each reduces platinum use and holds up effectively in gas cell testing. The catalyst, comprised of alloying platinum with cobalt in nanoparticles, was proven to beat US Division of Power (DOE) targets for the yr 2020 in each reactivity and sturdiness, in accordance with exams described within the journal Joule.
Stabilizing transition metals (M) in MPt alloy below acidic circumstances is difficult, but essential to spice up Pt catalysis towards oxygen discount response (ORR). We synthesized ∼9 nm hard-magnet core/shell L1 Zero-CoPt/Pt nanoparticles with 2–three atomic layers of strained Pt shell for ORR.
At 60°C in acid, the hard-magnet L1 Zero-CoPt higher stabilizes Co (5% loss after 24 hr) than soft-magnet A1-CoPt (34% loss in 7 hr). L1 Zero-CoPt/Pt achieves mass actions (MA) of Zero.56 A/mg Pt initially and Zero.45 A/mg Pt after 30,000 voltage cycles within the membrane electrode meeting at 80°C, exceeding the DOE 2020 targets on Pt exercise and sturdiness (Zero.44 A/mg Pt in MA and—Li et al.
A brand new catalyst developed at Brown combines an outer shell of platinum atoms (gray spheres within the rendering on the correct) with ordered layers of platinum and cobalt atoms (blue spheres) in its core. The ordered layers assist to tighten the shell and defend the cobalt, which makes that catalyst extra reactive and sturdy. Solar lab / Brown College
The sturdiness of alloy catalysts is a giant situation within the discipline. It’s been proven that alloys carry out higher than pure platinum initially, however within the circumstances, inside a gas cell the non-precious steel a part of the catalyst will get oxidized and leached away in a short time.—Junrui Li, lead writer
To deal with this leaching drawback, Li and his colleagues developed alloy nanoparticles with a specialised construction. The particles have a pure platinum outer shell surrounding a core comprised of alternating layers of platinum and cobalt atoms. That layered core construction is essential to the catalyst’s reactivity and sturdiness, says Shouheng Solar, professor of chemistry at Brown and senior writer of the analysis.
The layered association of atoms within the core helps to clean and tighten platinum lattice within the outer shell. That will increase the reactivity of the platinum and on the identical time protects the cobalt atoms from being eaten away throughout a response. That’s why these particles carry out so significantly better than alloy particles with random preparations of steel atoms.—Shouheng Solar
The main points of how the ordered construction enhances the catalyst’s exercise are elucidated in a separate laptop modeling paper revealed within the Journal of Chemical Physics. The modeling work was led by Andrew Peterson, an affiliate professor in Brown’s College of Engineering, who was additionally a coauthor on the Joule paper.
For the experimental work, the researchers examined the flexibility of the catalyst to carry out the oxygen discount response, which is essential to the gas cell efficiency and sturdiness. On one aspect of a proton alternate membrane (PEM) gas cell, electrons stripped away from hydrogen gas create a present that drives an electrical motor. On the opposite aspect of the cell, oxygen atoms take up these electrons to finish the circuit. That’s executed by the oxygen discount response.
Preliminary testing confirmed that the catalyst carried out effectively within the laboratory setting, outperforming a extra conventional platinum alloy catalyst. The brand new catalyst maintained its exercise after 30,000 voltage cycles, whereas the efficiency of the normal catalyst dropped off considerably.
However whereas lab exams are essential for assessing the properties of a catalyst, the researchers say, they don’t essentially present how effectively the catalyst will carry out in an precise gas cell. The gas cell setting is way hotter and differs in acidity in comparison with laboratory testing environments, which might speed up catalyst degradation. To learn how effectively the catalyst would maintain up in that setting, the researchers despatched the catalyst to the Los Alamos Nationwide Lab for testing in an precise gas cell.
The testing confirmed that the catalyst beats targets set by the Division of Power (DOE) for each preliminary exercise and longer-term sturdiness. DOE has challenged researchers to develop catalyst with an preliminary exercise of Zero.44 amps per milligram of platinum by 2020, and an exercise of at the least Zero.26 amps per milligram after 30,000 voltage cycles (roughly equal to 5 years of use in a gas cell automobile). Testing of the brand new catalyst confirmed that it had an preliminary exercise of Zero.56 amps per milligram and an exercise after 30,000 cycles of Zero.45 amps.
Even after 30,000 cycles, our catalyst nonetheless exceeded the DOE goal for preliminary exercise. That sort of efficiency in a real-world gas cell setting is absolutely promising.—Shouheng Solar
The researchers have utilized for a provisional patent on the catalyst, and so they hope to proceed to develop and refine it.
The work was supported by the DOE’s Power Effectivity and Renewable Power, Gasoline Cell Applied sciences Workplace.
Junrui Li, Shubham Sharma, Xiaoming Liu, Yung-Tin Pan, Jacob S. Spendelow, Miaofang Chi, Yukai Jia, Peng Zhang, David A. Cullen, Zheng Xi, Honghong Lin, Zhouyang Yin, Bo Shen, Michelle Muzzio, Chao Yu, Yu Seung Kim, Andrew A. Peterson, Karren L. Extra, Huiyuan Zhu, Shouheng Solar (2018) “Laborious-Magnet L1Zero-CoPt Nanoparticles Advance Gasoline Cell Catalysis” Joule doi: 10.1016/j.joule.2018.09.016