Michael Grätzel’s laboratory at EPFL has successfully produced hydrogen fuel from sunlight and water. By combining a pair of solar cells made with a mineral called perovskite and low cost electrodes, scientists have obtained a 12.3 percent conversion efficiency from solar energy to hydrogen.
>At the Laboratory of Photonics and Interfaces at EPFL, led by Michael Grätzel, where scientists invented dye solar cells that mimic photosynthesis in plants, they have also developed methods for generating fuels such as hydrogen through solar water splitting. To do this, they either use photoelectrochemical cells that directly split water into hydrogen and oxygen when exposed to sunlight, or they combine electricity-generating cells with an electrolyzer that separates the water molecules.
Their device converts into hydrogen 12.3 percent of the energy diffused by the sun on perovskite absorbers – a compound that can be obtained in the laboratory from common materials.
>”Both the perovskite used in the cells and the nickel and iron catalysts making up the electrodes require resources that are abundant on Earth and that are also cheap,” explained Jingshan Luo. “However, our electrodes work just as well as the expensive platinum-based models customarily used.”
> “Once you have hydrogen, you store it in a bottle and you can do with it whatever you want to, whenever you want it,” said Michael Grätzel. Such a gas can indeed be burned – in a boiler or engine – releasing only water vapor. It can also pass into a fuel cell to generate electricity on demand. And the 12.3% conversion efficiency achieved at EPFL “will soon get even higher,” promised Grätzel.
More powerful cells
>“A voltage of 1.7 V or more is required for water electrolysis to occur and to obtain exploitable gases,” explained Jingshan Luo. To get these numbers, three or more silicon cells are needed, whereas just two perovskite cells are enough. “This is the first time we have been able to get hydrogen through electrolysis with only two cells!” Luo adds.