An inexhaustible source of hydrogen without the need for electricity and completely carbon neutral. It sounds too good to be true, but in this case it appears it is not, as Penn State engineers have developed a method to do just that.
Recent developments in hydrogen production and storage have already made hydrogen a promising alternative to gasoline. But this new find may lead to one of the most important clean sources of hydrogen, since it has a major advantage over other sources: it doesn’t need a clean water source. In fact it cleans wastewater in the process.
The technique presented in the Proceedings of the National Academy of Sciences is based on microbial electrolysis cells. The microbes in these cells can produce and electric current by consuming organic matter.
To produce a usable amount of electricity however too many of the cells have to be stacked to be practical. Hydrogen has also previously been produced with the cells as well, but to do so an extra electrical input was needed to reach the 0.414 volts needed to convert water into hydrogen and oxygen.
The microbes by itself can produce around 0.3 volts, so they are just short of the threshold needed to create hydrogen. But by combining them with reverse-electrodialysis (RED), which extracts energy from the ionic differences between fresh and salt water, the voltage was upped to about 0.5 volts, easily enough to produce hydrogen.
So in short we need a place where salt water meets fresh water, some bacteria and carbon containing wastewater like sewage and in return we get a practically limitless supply of hydrogen? Sounds like a good deal.
Expensive or not?
So what is the drawback? Well it has one: it is expensive, at least so far. Since the research team used platinum as a catalyst to split the water into hydrogen and oxygen. But to make the picture perfect, the team has already come up with another material for the catalyst: the cheap and abundant molybdenum sulphide.
Its only drawback is its lower efficiency of 51 per cent as opposed to the 58 to 64 per cent of platinum. But 51 per cent efficiency is not at all bad for a limitless source of hydrogen.
© Jorn van Dooren | www.bitsofscience.org