New energy worries have increased the focus on hydrogen, the earth’s most abundant element. But, says MIT’s Daniel Nocera, there’s been too little attention given to the problem of obtaining this first-rate fuel.
Relying on fossil fuels to produce hydrogen could pose both environmental and, ultimately, supply problems, he says. But employing electricity to electrolytically break down water into hydrogen and oxygen has flaws, too: “you’ll use more electricity than you could generate from the hydrogen and oxygen you produce.”
Nocera, a professor of chemistry, has a more sustainable approach: create hydrogen the way plants do, through a variation on the natural process called photosynthesis.
In photosynthesis, plants take in carbon dioxide – the stuff we exhale – and water. From these, and with the crucial addition of sunlight, they create oxygen and carbohydrates. But along the way, they’re actually making hydrogen. Nocera’s concept is an artificial system that does what plants do, but stops the chemical reactions at the point where you have pure hydrogen rather than the bound version found in carbohydrates.
If he succeeds, our energy problems would be over. Since his system would harness the sun’s power – and since the sunlight reaching Earth in a given 24-hour period represents thirty years’ worth of the energy needed for all human activities – our hydrogen supplies would essentially be limitless.
The problem is finding an efficient way to mimic plants. “Remember, it took 2 billion to 4 billion years for photosynthesis to evolve,” he notes.
“It’s a very complex process.” So complex few scientists have tried to develop their own variants. Nocera, though, has made it his core goal. And over a period of ten-years plus, he’s had some key successes.
One involves the basic science of photosynthesis. “There’s a problem in biology called proton- coupled electron transfer,” he notes. “Several years ago, my lab published a paper on it, and now this area of chemical biology is a sort of cottage industry in that field.”
The scientist has also made a key advance in more practical terms. Deploying a specially designed molecule, he showed he could use light to separate out the hydrogen bound up in a substance that’s one of a class of hydrogen-bearing compounds known as hydrohalic acids.
Though a fellow chemist at Michigan State hailed the achievement as proof you can use light to move a stable hydrogen-bearing compound into a higher energy state – and, critically, can come up with pure hydrogen in the process – tough hurdles lie ahead. Should Nocera overcome these, though, amazing possibilities could open up.
An example is power systems that are wholly self-sustaining. “If I live in the desert,” he notes, “and I’m making all my hydrogen and oxygen from water, I’d only need to truck in my water supply once. After that, the system will turn the hydrogen and oxygen back into water, so it will be completely self-sufficient.” Nocera concedes that such scenarios lie far in the future, but he says he’s committed to making them a reality.
Is it a daunting challenge? “Yes it is,” he concedes. “But it’s also a crucial problem, and if you’re at MIT, that’s the kind of problem you should be working on.”