This reality is inching ever closer after researchers from the Royal Melbourne Institute of Technology (RMIT) in Australia developed a "solar paint" capable of pulling water vapor from the air and splitting it into hydrogen and oxygen using energy provided by sunlight.
"Hydrogen is one of the cleanest fuels, since it turns into water when burned," Daeneke told ResearchGate. "Hydrogen can be used either in fuel cells or directly in combustion engines. The first hydrogen fueled cars and busses can already be found in some cities around the globe. The key advantage here is that no harmful side products are emitted. This can drastically reduce smog, which is a serious issue in today's megacities, and greenhouse gases if the hydrogen is produced from renewable energy sources."
The paint contains a new, silica-gel-like compound—synthetic molybdenum-sulphide—that not only absorbs moisture from its surroundings but can also trigger chemical reactions that splits water molecules into hydrogen and oxygen atoms.
"We found that mixing the compound with titanium oxide particles leads to a sunlight-absorbing paint that produces hydrogen fuel from solar energy and moist air," Daeneke said in a statement. "Titanium oxide is the white pigment that is already commonly used in wall paint, meaning that the simple addition of the new material can convert a brick wall into energy harvesting and fuel production real estate."
The technology is also ideal because the hydrogen created by the solar paint is not produced by fossil fuels nor is a constant supply of clean water necessary.
"The technique we developed avoids the use of liquid water altogether," Daeneke explained to ResearchGate. "Instead, our system captures water vapor from air ... This avoids all of the issues arising from the use of liquid water."
Theoretically, the solar paint could be applied or sprayed onto any surface where water vapor is present. Even evaporated moisture from salty or waste water would be sufficient, Daeneke noted.
Kourosh Kalantar-zadeh, a professor at RMIT, added that "this system can also be used in very dry but hot climates near oceans. The sea water is evaporated by the hot sunlight and the vapor can then be absorbed to produce fuel."
Daeneke envisions that the paint could one day be used in conjunction with other renewable energy technologies.
"Photocatalytic paints may find application in multiple settings, one obvious one could be the local production of hydrogen as an energy carrier, side by side with photovoltaics generating renewable electricity," he told ResearchGate. "Further steps are necessary in order to fully see the scope of this technology. For example, our next targets are to incorporate this system together with gas separation membranes that will allow selectively harvesting and storing the produced hydrogen."
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