New paint material can harvest hydrogen fuel from the air

Hydrogen is one of the cleanest fuels around, and now evaporated water molecules provide an endless source.

Researchers have developed a paint-like product that can turn air into hydrogen fuel. Hydrogen is an extremely clean fuel source, emitting only water when it’s burned. However, the fossil fuels needed to create it negate its environmental benefits, and alternative production methods using liquid water aren’t cost-effective. The newly developed material addresses both problems, drawing water molecules from humid air and using solar energy captured by the paint to split them into their hydrogen and oxygen components. We spoke with Torben Daeneke, author of the study introducing the technology, to learn more.

ResearchGate: Why is hydrogen fuel useful?

Torben Daeneke: Hydrogen is one of the cleanest fuels, since it turns into water when burned. 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.

Apart from its use as an energy carrier, hydrogen is also a key chemical that is used in many industrial processes, like fertilizer production, microelectronics, and pharmaceuticals. Hydrogen also finds applications in the food industry, for example in the production of margarine. Overall the applications of hydrogen gas are diverse, and finding better ways to produce it will have a positive impact on our future.

RG: How is hydrogen fuel typically produced?

Daeneke: Unfortunately, today’s dominant method of hydrogen production uses fossil fuels to create hydrogen in a process called steam reforming. This process produces significant amounts of greenhouse gasses which negate any environmental benefit of a future hydrogen based economy. This fact is the main reason why new ways of producing hydrogen are required.

RG: Why aren’t cleaner methods of producing hydrogen used more widely?

Daeneke: Hydrogen can be produced using electrolysis, where two electrodes are placed into liquid water and a voltage is applied. Many people will remember doing this as an experiment in high school. Unfortunately, this process is quite inefficient, and expensive platinum-based catalysts are required to increase efficiency. Furthermore, liquid water can be difficult to work with. It requires pumping equipment, must be purified, and is prone to forming little gas bubbles on the surface of the electrodes, which reduce the amount of hydrogen that can be produced in a given timeframe.

RG: How can the technique you’ve developed help?

Daeneke: The technique we developed avoids the use of liquid water altogether. Instead, our system captures water vapor from air, which is then converted into hydrogen and oxygen using energy provided by sunlight. This avoids all of the issues arising from the use of liquid water. The process is also water neutral, meaning that no drinking water is required—the evaporated moisture coming off salty or waste water will be sufficient. Since no fluid handling equipment is needed and no electrodes are required, this system is significantly simpler than existing concepts, which is one of the key aspects of this work.

RG: How does it work?

Daeneke: Our solar paint consists of two components: a moisture absorbing catalyst we developed and light absorbing titanium oxide. The titanium oxide particles absorb light from the sun and convert it into electric energy. Since the titanium oxide is in close contact with the moisture absorbing catalyst, this captured solar energy can be directly transferred into the catalyst, where it is used to split water and produce hydrogen. Our developed catalyst has the ability to absorb more moisture from humid air, which results in its ability to continuously split water using the energy provided by the sun. The hydrogen needs to then be captured for storage and later use.

RG: How could a paint like this one day be used?

Daeneke: 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. 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.

The catalyst may also be integrated into complex systems, where the produced hydrogen is directly used in following chemical reactions to create more complex chemicals. Similar processes already occur in plants, where solar energy is converted into complex sugar molecules.

RG: Is there an application that excites you in particular?

Daeneke: For me as a chemist and material scientist, the prospect of combining two separate material properties in order to achieve completely new functionality is very exciting. In this case we are using both, the newly discovered moisture harvesting and catalytic capabilities of molybdenum sulphide, in order to solve the technological challenge of producing hydrogen in a complete new way. From a scientific view this is very interesting. I would like to see the technology being used in the future, creating green fuels for our society.


Featured image courtesy of Jakob Owens.