Clean Transport tungsten sulfide (WS2) could be fuel cell catalyst

Published on July 27th, 2013 | by Tina Casey


Weird Fuzzy Compound Could Be Next Big Fuel Cell Catalyst

July 27th, 2013 by  

Viewed up close, tungsten sulfide looks like a bunch of sea urchins moshing at a foam party, but this chemical compound could become the next workhorse of the hydrogen fuel cell field. A team of researchers from Rutgers University is on track to develop nanoscale sheets of tungsten sulfide as a low cost replacement for platinum catalysts in fuel cells, and that could help push the electric vehicle market out of reliance on expensive lithium-ion batteries and into a more affordable format. No worries for Tesla EV fans, though, at least not yet. The research is still in its early stages and meanwhile the nation’s EV battery charging network has been skyrocketing.

A Low Cost Hydrogen Fuel Cell Catalyst

Just last week we were talking about the affordability obstacles faced by hydrogen fuel cells, and the catalyst is the big one. Currently the catalyst of choice is platinum, so the hunt has been on for low-cost alternatives.

Tungsten sulfide (WS2) is of interest because of its inorganic nanotube structure, and it is already in use as a catalyst in reactions such as hydrodesulfurization. It occurs naturally in tungstenite, which is a rare mineral, but it can also be synthesized in a variety of ways.

According to the Rutgers team, WS2 is among a group of compounds that are promising, but lack efficiency due to their relatively low number of active sites.

To increase the number of sites and boost their activity level, the team took a page out of the graphene book. Graphene is a superstrong “miracle material” only one atom thick, originally obtained through a crude form of exfoliation. The team that discovered graphene literally lifted a layer from the surface of a chunk of graphite with sticky tape.

The exfoliation process used by the Rutgers team was somewhat more sophisticated, but the idea was similar: take a chunk of bulk material and lift a nanoscale sheet from the surface.

As described by writer Belle Dumé in, the result was a structure never studied before, a sheet of WS2 only three atoms thick with the tungsten atom wedged between the sulphur atoms (keep in mind that graphene consists only of carbon, therefore a single-atom layer is possible in graphene but not in WS2).

So far, tests have shown that the WS2 sheets produce a level of catalytic activity far greater than would be expected, given how extremely thin they are. The obvious result is that very little of the compound would be needed to coat a surface, resulting in lower costs.

Fuel Cells VS Batteries

As for whether fuel cells or batteries will eventually dominate the EV market, the jury is still out. If costs keep dropping for both formats, the result could be a far more diverse and flexible vehicle market than petroleum fuel currently permits, with both commercial and individual buyers being able to tailor their choices more precisely to their actual driving patterns.

The Obama Administration has been betting on both sides, though so far in terms of research dollars batteries seem to be winning out, with the Administration providing a hefty boost to EV battery research through the JCESR initiative. A more modest effort has gone into fuel cell electric vehicle development, through the public-private H2USA initiative as well as a number of Department of Defense and DOE programs.

On the other hand, one focus of JCESR is on new flow battery technology, and other formats such as zinc-air are coming close to commercialization, so the payout for that initiative won’t necessarily fall to lithium-ion batteries alone.

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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

  • Dan Hue

    I think that batteries and fuel cells are complementary. Batteries have a low energy density and recharge slowly, but they are very efficient. The energy density will improve, but won’t rival liquid fuels anytime soon, and the bigger the battery, the longer it takes to charge. Fast charging is possible, but it seems to hurt longevity if done too frequently. I don’t see battery swapping taking on, but then I may lack vision there. By comparison, and assuming an all renewable energy economy, the production of hydrogen for fuel cells is not efficient, but once obtained, it can be stored and provides all the advantages of the current liquid (or gas) fossil fuel-based economy. I can see how that will lead to batteries as the primary energy storage device for cars and trucks, for 90+% of typical transportation needs, and for those who need extended range, a fuel cell to complement it. I don’t know of the economics of such a design, but it seems elegant to me. Disclaimer: I own a Volt and while I love the ER capability, I also hate it when the gas engine turns on.

    • Bob_Wallace

      Some people think fuel cells are competing against batteries for personal transportation. I don’t think that’s a competition fuel cells are going to win.

      I think the more reasonable role for fuel cells is as a ICE replacement.

      The other possible role for fuel cells is deep backup for the grid. If we can produce hydrogen efficiently from water and store it economically then we could use hydrogen fuel cells for periods of low wind and sunshine.

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