Sandia National
Laboratories post-doctoral fellow Stan Chou
demonstrates the
reaction of more efficiently catalyzing hydrogen.
In this
simulation, the color is from dye excited by light and generating electrons
for the catalyst
molybdenum disulfide to evolve hydrogen. (Photo by Randy Montoya)
‘Green’ process runs on sunlight
(October 7, 2015) Sandia
National Laboratories researchers seeking to make hydrogen a less expensive
fuel for cars have upgraded a catalyst nearly as cheap as dirt — molybdenum
disulfide, “molly” for short — to stand in for platinum, a rare element with
the moonlike price of $1,500 a gram.
Sandia-induced changes elevate the plentiful,
37-cents-a-gram molly from being a welterweight outsider in the energy-catalyst
field — put crudely, a lazy bum that never amounted to much — to a possible
contender with the heavyweight champ.
The improved catalyst, expected to be the subject of an Oct.
7 Nature Communications paper, has already released four times the amount of
hydrogen ever produced by molly from water. To Sandia postdoctoral fellow and
lead author Stan Chou, this is just the beginning: “We should get far more
output as we learn to better integrate molly with, for example, fuel-cell
systems,” he said.
An additional benefit is that molly’s action can be
triggered by sunlight, a feature which eventually may provide users an
off-the-grid means of securing hydrogen fuel.
Hydrogen fuel is desirable because, unlike gasoline, it
doesn’t release carbon into the atmosphere when burned. The combustion of
hydrogen with oxygen produces an exhaust of only water.
In Chou’s measured words, “The idea was to understand the
changes in the molecular structure of molybdenum disulfide (MOS₂),
so that it can be a better catalyst for hydrogen production: closer to platinum
in efficiency, but earth-abundant and cheap. We did this by investigating the
structural transformations of MOS₂ at the atomic scale, so that all
of the materials parts that were ‘dead’ can now work to make H₂
[hydrogen].”
Sandia National
Laboratories researchers, from right, Stan Chou, Bryan Kaehr,
Jeff Brinker, Ping
Lu and Eric Coker, gather in a lab where work on the catalyst
molybdenum
disulfide was achieved. (Photo by Randy Montoya)
The rind of an orange
in what sense were the parts “dead,” one might ask?
Visualize an orange slice where only the rind of the orange
is useful; the rest — the edible bulk of the orange — must be thrown away.
Molly exists as a stack of flat nanostructures, like a pile of orange slices.
These layers are not molecularly bolted together like a metal but instead are
loose enough to slide over one another — a kind of grease, similar to the
structure of graphene, and with huge internal surface areas.