As outlined in Monday’s news, platinum is a world-class catalyst but remains a cost hurdle for fuel cell production. Now, in research outlined in Nature Communications, Sandia National Laboratory scientists have moved away from platinum as a catalyst entirely, turning instead to a cheaper substitute. Molybdenum disulphide, MoS2 or ‘molly’ for short, an inorganic compound similar to graphite, and currently available at less than a hundredth of the price of platinum.
In laboratory conditions MoS2 has been shown to provide a catalytic efficiency approaching platinum’s, but only at the edge of its 2d crystal nanostructure. The interior of the MoS2, which makes up the vast majority of a given sample, is differently structured and unreactive with hydrogen. As a catalyst therefore, MoS2 was 90% dead weight.
However, by using lithium to ‘pull apart’ the sheets of a MoS2 lattice, the Sandia team were able to increase the material’s surface area and, more importantly, produce a change in structure that activated the catalytic properties of the interior.
To a degree, this upgrade effect has been recognised since 1973, but the mechanisms involved were poorly understood and difficult to replicate. The Sandia team’s advance is to map exactly how and why the improved catalyst works, and thus pave the way for using MoS2 in industrial hydrogen production.
“It’s photosynthesis, but using inorganic materials rather than plants,” lead author Stan Chou explained. “Plants use enzymes powered by sunlight to break up water into hydrogen and oxygen in a delicate process. We’re proposing a similar thing here, but in a more rapid reaction and with sturdier components.”
The team claims that their upgraded Molly has already increased the yield of hydrogen production by over four times. If replicated, their model could see a big price drop in fuel cell costs going forward.
Source: Nature Communications 6, Article number: 8311 (free to public)