In science’s quest to develop less polluting sources of energy, hydrogen gas has often been used as an example as a potential replacement for fossil fuels: aside from being the most abundant substance in the universe, it is also the most combustible natural substance known, and only produces pure water when burned with oxygen. Unfortunately, the chemical instability of its gaseous form means that storing it is inherently hazardous, and the extraction of the gas from hydrogen’s more stable forms, such as water or petroleum products, can be highly energy inefficient, or produce a disproportionate amount of waste pollutants.

However, researchers with Australia’s Royal Melbourne Institute of Technology (RMIT University) have developed a paint that can be applied to virtually any surface that can draw moisture from the air and, when activated by sunlight, separates the water’s hydrogen and oxygen molecules, for collection as a potential fuel source.

The new substance uses a synthetic molybdenum-sulphide compound as a catalyst to facilitate the extraction: molybdenum sulphide already readily absorbs moisture from the air, in a manner much like the silica gel packs that are found in many consumer product packages. The material is also a semiconductor that, when exposed to sunlight, splits the hydrogen and oxygen atoms from the absorbed moisture, which can be collected and stored for later use.

"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," explains RMITs Dr Torben Daeneke. Titanium oxide is a compound already commonly used as a pigment to produce white paint.

"Our new development has a big range of advantages," Daeneke continues. "There’s no need for clean or filtered water to feed the system. Any place that has water vapour in the air, even remote areas far from water, can produce fuel."