Fuel cell electric vehicles have a lot of catching up to do compared to their battery-powered cousins, but it’s also becoming clear that the learning curve for hydrogen fuel cells is accelerating past the fossil fuel stage and racing into renewable energy, as indicated by a new low-cost catalyst under development by our molly-loving friends over at Sandia National Laboratories.
Fossil Fuels, FCEVs, and BEVs
One of the central stumbling blocks for fuel cell electric vehicles (FCEVs) is the use of fossil natural gas to produce hydrogen fuel. In that regard, FCEVs face a challenge similar to that faced by battery EVs (BEVs), which depend on fossil sources when they are charged from a grid mix that includes coal or natural gas (or to a much lesser extent in the US, petroleum). However, FCEVs are practically always much dirtier due to lower efficiencies, and can’t be fueled of rooftop solar power.
BEVs are resolving their fossil problem at a fairly rapid clip in some markets anyway, as more utilities adopt renewable wind and solar energy on top of the considerable hydro resources at hand in some parts of the US. Distributed solar is making its way directly to home charging stations as well as public ones. Micro wind turbines and combined wind and solar systems are also finding a place in the EV charging station field.
Similarly, renewable energy is also making its way into hydrogen fuel production for FCEVs, primarily in the form of electrolysis (water-splitting) powered directly by the sun, or indirectly by wind-generated electricity. Emerging power-to-gas systems are also leveraging renewable energy to use hydrogen gas as a utility-scale storage system.
The Road To Low Cost Hydrogen Fuel
Renewable energy or not, the problem with splitting water to produce hydrogen fuel comes down to cost. The process requires a catalyst (or two, for those of you keeping score at home). The conventional catalyst of choice is platinum, which currently weighs in at a hefty $1,500 per gram.
Aside from cost, platinum is also problematic in the US due to supply chain issues. Though the US is a leading platinum-producing country, South Africa and Russia beat it by a mile. It’s certainly not the kind of abundant hat you’d want to hang your domestic auto industry on.
Molly To The Rescue
The race is on for low-cost alternatives in the US, and that brings us right around to the new FCEV development from Sandia. Researchers there have been setting their sights on “molly,” short for molybdenum disulfide (or MoS2 if you’re not making a party drug joke out of it).
MoS2 has two points in its favor here in the US: it currently costs just 37 cents per pound, and it can be produced from abundant domestic sources, namely molybdenite.
If MoS2 is ringing bells, that’s because the material is emerging as a 2D “cousin” of graphene, and research teams have been investigating it for energy storage as well as renewable hydrogen production and other clean tech applications.
The secret sauce is an “energetically disordered region” at the edges of the 2D crystals, which translates into a catalytic efficiency pretty close to that of platinum.
Our sister site Gas2.org noted a variation on that theme back in 2010, when researchers there described a molybdenum-oxo catalyst for water-splitting.
At Sandia, researchers have been focused on making the most out of the aforementioned disordered region. While tantalizingly efficient as a catalyst, the problem is that this nanoscale region has to drag along an enormous tail of relatively useless material.
The Sandia team describes it as similar to an orange, but in reverse: the thin rind is the useful part, while the edible pulp is totally useless. That presents a significant roadblock to commercialization.
The team describes the path toward a solution in the November 7 edition of the journal Nature, under the title “Understanding catalysis in a multiphasic two-dimensional transition metal dichalcogenide.”
The basic idea is to render the “pulp” catalytically active, and the team demonstrated proof of principle for accomplishing that by using lithium to separate nanoscale sheets of MoS2 in solution. The lithium-enabled process changes the molecular “lattice” into an active structure, like that of the edge.
“Clean Diesel” Scandal Helps The Case For FCEVs
On the heels of the Volkswagen diesel emissions scandal, new evidence has emerged that many other diesel models in the EU have used “teach to the test” engineering, enabling cars to meet nitrogen oxides (NOx) standards in the lab but emitting an average of four times more — and up to 20 times in at least one case — during actual road use.
Industry observers are already anticipating that the case for “clean diesel” has gone down the tubes because of Volkswagen, and the new cases point to the increasingly complex — and expensive — task of developing testing regimens that accurately measure pollutants under real road conditions.
While it’s true that FCEV technology is far behind BEVs, energy planners in some European countries (Germany is a good example) are already banking on power-to-gas technology to store renewable energy and replace petroleum fuel, and the elimination of “clean diesel” could push that trend along.
Image (cropped) by Randy Montoya, via Sandia National Laboratories.