UCLA team designs graphene-nanopocket caged PtCo nanocatalysts for fuel cells; very durable, ultra-low loading

UCLA researchers, with colleagues at UC Irvine, have designed a graphene-nanopocket caged platinum-cobalt ([email protected]) nanocatalyst for fuel cells with good electrochemical accessibility and exceptional durability under a demanding ultra-low PGM load (0.070 mgPGM cm–2) due to the contactless enclosure of the graphene nanopockets.

[email protected] delivers a peak mass activity of 1.21 A mgPGM-1a nominal power of 13.2 W mgPGM-1 and 73% activity mass retention after accelerated durability testing. With the greatly improved power rating and durability, researchers project a weight of 6.8gPGM charging for a 90 kW PEMFC vehicle; charging approaches used in a typical catalytic converter.

An article about their work appears in the journal Nature’s nanotechnology.

Graphene-wrapped alloy produced 75 times more catalytic activity 65% ​​more power ~20% more catalytic activity at the end of expected fuel cell life ~35% loss of power less power after tests that simulate 6,000-7,000 hours of use, beating the 5,000 hour target for the first time. Credit: Huang UCLA Group


This has never been done before. This discovery involved a certain chance. We knew we were onto something that could make smaller particles stable, but we didn’t expect it to work so well.

—corresponding author Yu Huang, professor and chair of the Department of Materials Science and Engineering at UCLA Samueli School of Engineering and member of the California NanoSystems Institute at UCLA

Today, half of the world’s total supply of platinum and similar metals is used for catalytic converters in fossil fuel-powered vehicles; somewhere between 2 and 8 grams of platinum is needed per vehicle. By comparison, current hydrogen fuel cell technology uses about 36 grams per vehicle.

At the lowest platinum load tested by Huang and his team, each hydrogen vehicle would only need 6.8 grams of platinum.

The researchers split the platinum-cobalt alloy catalyst into particles with an average length of 3 nanometers; smaller particles mean more surface area, and more surface area means more space where catalytic activity can occur. However, smaller particles are also much less durable, as they tend to detach from a surface or clump together into larger particles.

Huang and his colleagues solved this limitation by arming their catalyst particles in graphene nanopockets, which prevented the particles from migrating. At the same time, graphene allowed a small gap of about 1 nanometer around each catalyst nanoparticle, which meant that key electrochemical reactions could occur.

This latest advancement follows a recent collaborative study led by Huang that produced a model for predicting the catalytic activity and durability of a platinum-based alloy that can be used to guide catalyst design, the first of its kind. gender. (Previous post.) She and her team are working to translate their experimental results into practical technology that can be commercialized.

The co-first authors of the study are postdoctoral researcher Zipeng Zhao and doctoral student Zeyan Liu, both from UCLA. Other UCLA authors are doctoral students Ao Zhang, Wang Xue, and Bosi Peng; and Xiangfeng Duan, professor of chemistry and biochemistry at UCLA College and member of CNSI. UC Irvine faculty member Xiaoqing Pan and his postdoctoral researcher Xingxu Yan assisted in imaging the graphene nanopockets.

The research received funding from the US Office of Naval Research.

Resources

  • Zhao, Z., Liu, Z., Zhang, A. et al. (2022) “Graphene-nanopocket caged PtCo nanocatalysts for highly durable fuel cell operation under demanding ultra-low Pt loading conditions” Nat. Nanotechnology. doi: 10.1038/s41565-022-01170-9