We use solar power to make electricity, but now thanks to new developments, we will be able to use it for hydrogen production. Now isn’t that cooking with gas, or what?
Hydrogen is currently produced from natural gas using a technique called steam reformation. So, if one makes a carbon accounting of hydrogen-powered cars, it’s not so different from using natural gas or liquified petroleum gas. Electrolysis of water isn’t an economical proposition, thanks to the atrocious energy balance, if you use electricity from the grid.
Directly producing hydrogen using solar power, however, helps us overlook this because the electricity used is freely given by the sun. And this is where stuff becomes interesting. Some tried making photoelectrochemical solar cells that directly split hydrogen and oxygen from water. Unfortunately, these babies are expensive because they use exotic materials. Another approach is to use solar cells with electrolyzers that do the splitting. Still a costly proposition even with falling prices of solar cells, and the high prices of the electrodes aren’t helping.
That is, until researchers at the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland tried to do something about it. Jingshan Luo and his colleagues recently made a device that electrolyzes hydrogen from water at 12.3% efficiency. That isn’t a bad start considering that the efficiency of commercial solar cells is around 20%. What’s even better is that they used cheap materials to produce the device, drawing inspiration from a rock called perovskite. They used a perovskite structure made from common metals, as opposed to single crystal silicon, to produce the solar cells. And the penny pinching didn’t stop there. They used electrodes made from nickel and iron, instead of using platinum which is more expensive than gold. (Which was why 80’s band Spandau Ballet was laughing their way to the bank when True, from which the single Gold came from, reached platinum back in the day).
What’s more, this high efficiency couldn’t be achieved using silicon cells because of limitations in their voltage. Silicon cells can only achieve an open circuit voltage of 0.7V whereas the perovskite cells that Luo and his team made was 1V. In order to electrolyze water, one has to generate at least 1.7V. So, you’d have to string together at least three silicon cells to get hydrogen from H2O, whereas Luo’s team has been able to do so with just two perovskite cells. “This is the first time we have been able to get hydrogen through electrolysis with only two cells!” Luo says.
The significance of this development was so much so that it deserved a space in the iconic journal Science recently.
Since this was initial work, efficiency will “soon get even higher” promised Prof. Michael Grätzel, head of the Laboratory of Photonics and Interfaces at EPFL where the device was invented.
Rock on, is all we can say, rock on!