What could be better than a solar cell that captures most of the visible light spectrum to generate energy? A cell that can capture the whole visible light spectrum and turn the energy into hydrogen. The cell is actually a molecule, and it is a busy molecule: it not only harnesses 50 percent more solar energy than existing solar cells, but it also turns this energy into hydrogen.
“The whole idea is that we can use photons from the sun and transform it into hydrogen. To put it simply, we are saving the energy from sunlight and storing it into chemical bonds so it can be used at a later time,” explains the lead researcher in the team that developed the molecule, chemistry professor Claudia Turro from the Ohio State University.
“What makes it work is that the system is able to put the molecule into an excited state, where it absorbs the photon and is able to store two electrons to make hydrogen,” Turro added. “This storing of two electrons in a single molecule derived from two photons, and using them together to make hydrogen, is unprecedented.”
The molecule is a form of rhodium—an inert metal and member of the platinum group—and because it can both collect solar energy and then act as a catalyst to turn it into hydrogen, it makes for a much more efficient fuel production system than existing alternatives, at least with respect to energy loss during the process of conversion of solar energy into hydrogen.
Energy loss is an important consideration in the production of hydrogen as energy loss leads to higher production costs, and high cost is one of the main obstacles to hydrogen becoming a mainstream fuel for cars. Yet even with the high costs, hydrogen is gaining popularity.
Hydrogen fuel cell shipments globally grew 40 percent last year, an energy consultancy reported earlier this month. That means 1.1 GW of fuel cells were delivered last year, up from 806 MW a year earlier, said E4tech, as quoted by Bloomberg.
“For heavy-duty vehicles, it’s becoming more and more apparent you can’t do everything with batteries and there needs to be a way to approach zero-emission driving,” said David Hart, director at the Swiss-based consultancy.
What’s more, as the hydrogen industry grows and research expands, costs are beginning to fall. Last year, for instance, a team of scientists from Lancaster University came up with a way to make hydrogen fuel tanks more compact but more energy dense, which also made them cheaper.
“The cost of manufacturing our material is so low, and the energy density it can store is so much higher than a lithium ion battery, that we could see hydrogen fuel cell systems that cost five times less than lithium ion batteries as well as providing a much longer range — potentially enabling journeys up to around four or five times longer between fill-ups,” the lead researcher, Professor David Antonelli, said at the time.
Indeed, on some points hydrogen fuel cells perform better than lithium ion batteries. For one thing, they don’t need charging. They are simply refilled with hydrogen, which takes as long as it takes to fill up a tank with gasoline. Hydrogen cars also have a longer range than most plug-in EVs. Their problem: there are too few of them to be priced competitively.
Combining solar power with hydrogen could become a major step along the way to making hydrogen fuel as mainstream as gasoline. There is a lot of work to be done yet, as Professor Turro warned, but what her team did is certainly promising: zero-emission hydrogen fuel produced from clean, cheap solar energy.