Making hydrogen

On the roads around the Bay Area in 2015, there’s a good chance Brandon Wood will spot one of the first commercially available hydrogen-powered passenger vehicles: Toyota’s 2015 FC (fuel cell) car.

The Toyota’s fuel cells will electrochemically combine hydrogen with oxygen to generate electricity, producing water as the only chemical emission.

However, drivers will probably fill up with hydrogen produced by reformulating natural gas produced through hydraulic fracturing, commonly called “fracking.”

“For the long term it’s not a good solution,” says Wood, a research scientist in the Quantum Simulations Group at Lawrence Livermore National Laboratory (LLNL). “It’s not carbon neutral. What people have been trying to do for a long time is to produce hydrogen with sunlight and water. The problem is that solar water-splitting is really, really hard to do efficiently” – the challenge that initially brought Wood to work at LLNL with his supervisor Eric Schwegler.

Since the late 1990s, researchers at DOE’s National Renewable Energy Laboratory have had some success in using advanced solar cell materials to capture photons from the sun and split liquid H₂O into hydrogen and oxygen gases. The problem: The expensive semiconductor materials quickly degrade, often in less than 24 hours.

In research published in 2013 in the Journal of the American Chemical Society, Wood and colleagues, including Schwegler, provided the first evidence of a link between atomic interface kinetics and solar catalyst durability and performance.

“We looked at the atomic-level interactions between the surface of the solar catalyst materials, the material that’s absorbing the light, and the water solution in which it’s immersed,” Wood says. “We found that (at the atomic level) in the more durable materials, there’s really fast proton hopping at the interface.”

Proton hopping is the movement of the positively charged hydrogen nucleus across a network of hydrogen bonds and, for Wood, the return of an old nemesis, studied in detail in his Ph.D. work.

“We’ve suggested that the existence or absence of this property is intimately connected to why the materials degrade,” Wood says. “And we’ve made some suggestions as to what could be done to potentially mitigate this” – research that led to the team’s 2014 EERE Hydrogen Production Research and Development Award.