A team of researchers at Brookhaven National Laboratory in Upton, New York, has opened the door to a future of clean, cheap hydrogen fuel by ditching a popular platinum catalyst in favor of one based on two low cost alternatives, nickel and molybdenum.
Until now, the manufacture of hydrogen gas has faced a huge and somewhat ironic obstacle: Though hydrogen gas is produced from a chemical reaction in plain water, one of the cheapest and most abundant substances imaginable, the most efficient catalyst for generating that reaction is platinum - which currently weighs in at a hefty $50,000 per kilogram price tag, and rising.
In contrast, nickel costs only $20 per kilogram. Molybdenum, a silvery gray metal, costs $32.
If successfully commercialized, the new catalyst could have a powerful impact on the price of hydrogen, leading the way to a new generation of emission-free hydrogen-fueled vehicles as well as hydrogen fuel cells for many other uses.
Drawing more juice out of nickel and molybdenum was a complex project that Brookhaven describes as “Goldilocks chemistry:”
“For a catalyst to facilitate an efficient reaction, it must combine high durability, high catalytic activity, and high surface area. The strength of an element’s bond to hydrogen determines its reaction level - too weak, and there’s no activity; too strong, and the initial activity poisons the catalyst.”
By itself, nickel is not nearly as efficient a catalyst as platinum. To get to that “just right” point, the team tried infusing a nickel-molybdenum combination with nitrogen.The nitrogen expanded the metals into two-dimensional, lattice-like forms, resulting in nanosheets of nickel-molybdenum-nitride.
The 2-D nanosheets provide far more surface area for the reaction, boosting the new catalyst’s performance beyond the team’s expectations.
Though developing the new catalyst was complicated, according to Brookhaven, the production of the nanosheets is a simple process that could easily be ramped up to a commercial level and used for the bulk manufacture of hydrogen.
Similar research is also being conducted at a more modest end of the spectrum by Daniel Nocera of Harvard University (formerly of MIT). Nocera has also been deploying a nickel-molybdenum compound combined with another relatively cheap material, zinc, to create a low cost catalyst for producing hydrogen gas.
Nocera’s signature device, which he calls an “artificial leaf,” is designed as a cheap source of clean, renewable energy for households in the developing world.
It consists of the catalyst and a pocket-sized solar cell that can be dropped in a jar of water placed in the sun. The solar cell provides electricity to power the reaction and produce hydrogen, which can be stored for use at night.