Solar paint could turn buildings into green hydrogen generators

Solar-powered paint capable of generating clean hydrogen fuel could turn houses and office buildings into green power stations, new research has teased. The handiwork of a team at the RMIT University in Australia, the key is a new compound that unexpectedly acts as a catalyst in a chemical reaction. First, the paint absorbs water; then, it splits that water up into hydrogen and oxygen.

Breaking apart water in that way isn't new, of course: indeed, it's one of the more straightforward ways of generating hydrogen gas. The problem is that it requires power to do so, which can make economically viable production of hydrogen questionable. What signals the RMIT research out is the power source it's relying upon.

That's solar power, which gives the synthetic molybdenum-sulphide the energy it needs. Described as being like silica gel – which is used in packaging, as it absorbs water from the air – the compound can be mixed with titanium oxide, a pigment already used in white paints. When in the presence of moist air, the resulting paint absorbs sunlight and water and gives off hydrogen gas.

"Our new development has a big range of advantages," RMIT lead researcher Dr Torben Daeneke said of the research. "There's no need for clean or filtered water to feed the system. Any place that has water vapor in the air, even remote areas far from water, can produce fuel."

For instance, tower blocks in humid cities could be given a second purpose as hydrogen generators. "This system can also be used in very dry but hot climates near oceans," team fellow Distinguished Professor Kourosh Kalantar-zadeh said. "The sea water is evaporated by the hot sunlight and the vapor can then be absorbed to produce fuel."

Hydrogen as a fuel source has some obvious attractions. Although hydrogen fuel-cells are complex, requiring lattices through which gasses are passed, and each coated with special chemicals, the result is simply electricity and pure water. That's already seen applications in hydrogen-powered cars, like Toyota's Mirai and Honda's Clarity Fuel Cell, which use high-pressure tanks of the fuel to get 300-400 miles of range, with zero-emissions.

However the drawback has historically been production and distribution. While hydrogen can be produced in a green manner, using solar, wind, hydroelectric, or other methods, it's commonly sourced from natural gas. Either way, it needs to be transported to end-users. Some automakers are experimenting with on-site production, using whatever natural resources are most available with "pop-up" mini factories. Even so, they're far more complex than this solar approach.