A new platform to produce hydrogen

Hydrogen energy via photocatalytic production promises sustainable green energy.

A. Floatable  photocatalytic platforms are composed of bilayer structures: a photocatalytic layer and a supporting layer. B. The porous structure of the platform. C. The porous structure of the platform features floatability.  | Photo Credit: Institute for Basic Science, Seoul, S. Korea

OF the several sources of alternative energy, hydrogen energy harvested through photocatalytic production is particularly attractive for the sustainable green energy it promises.

Accordingly, a great amount of research has been done to enhance the intrinsic reaction efficiency of photocatalysts. However, an optimal platform, which is critical for their practical application and commercialisation, has not yet been realised. Current systems fix catalyst powder or nanoparticles onto different surfaces, such as particulate sheet-type, film-type, and flat panel-type platforms, which are submerged under water. Such systems face practical issues such as leaching of catalysts, poor mass transfer, and reverse reactions. They also require additional devices to separate and collect the generated hydrogen from the water, which adds to the complexity of the device and increases the cost.

Now a research team at the Center for Nanoparticle Research in the Institute for Basic Science, Seoul, South Korea, led by Taeghwan Hyeon has developed a new type of photocatalytic platform for the mass production of hydrogen. The work was published in a recent issue of Nature Nanotechnology. The new platform has an upper photocatalytic layer and a lower supporting layer. Both layers are composed of a porous structural polymer that gives the platform a high surface tension. In addition, it is fabricated in the form of a cryo aerogel, a solid substance filled with gas, which enables it to float on water.

The clear advantages of this platform over conventional ones include prevention of light attenuation by water, resulting in efficient solar energy conversion; easy diffusion of hydrogen gas into air, thus avoiding reverse oxidation reactions and preserving high reaction yield; the easy supply of water to the catalysts located inside the elastomer- hydrogel matrix due to its porosity; and, finally, stability of catalysts—as they are immobilised inside the matrix—for long-term operation without leaching issues.

The researchers have demonstrated the superior hydrogen production of the floatable platform compared with the conventional ones.

Furthermore, the platform’s scalability, which is essential for potential industrialisation, was demonstrated under natural sunlight. The experiment showed that the floatable photocatalytic platform using titania catalysts and a single copper atom with an area of 1 m² could produce about 80 ml of hydrogen. “The proposed platform can even produce hydrogen from solutions that dissolve household waste, such as polyethylene terephthalate bottles,” said Jeong Hyun Kim, a member of the team. “Consequently, the platform can be a solution for recycling wastes.” Significantly, this study also presents a generalised platform for efficient photocatalysis and is not limited to hydrogen production.