(Nanowerk News) A research team led by Prof. HYEON Taeghwan at the Nanoparticle Research Center within the Institute for Basic Science (IBS) in Seoul, South Korea has developed a new photocatalytic platform for the mass production of hydrogen. The group’s studies on the photocatalytic platform led to the development of a floatable photocatalytic matrix, which enables efficient hydrogen evolution reactions with clear advantages over conventional hydrogen production platforms such as film or panel types.
The research has been published in Natural Nanotechnology (“A floatable photocatalytic hydrogel nanocomposite for large-scale solar hydrogen production”).
The importance of alternative energy has recently increased due to global challenges such as environmental pollution and climate change. Among several potential alternative energy sources, hydrogen energy harvested by photocatalysis is highly highlighted for sustainable green energy production. Therefore, much research and development has been carried out to improve the intrinsic reaction efficiency of photocatalysts. However, research on the form factor of photocatalytic systems, which is very important for their practical application and commercialization, has not been actively explored.
Typically, present-day systems fix catalyst powder or nanoparticles onto different surfaces, such as particulate sheet-type, film-type, and flat-panel-type platforms, which are submerged underwater. They also face practical problems such as catalyst leaching, poor mass transfer and back reactions. They also require additional devices to separate and collect the hydrogen generated from the water, which adds to the complexity of the devices and increases costs.
The team at the Center for Nanoparticle Research in IBS, led by Prof. Hyeon, designed a new type of photocatalytic platform that floats on water for efficient hydrogen production. The new platform has a bilayer structure, consisting of an upper photocatalytic layer and a lower supporting layer (Fig. 1A). Both layers consist of a porous structural polymer that provides high surface tension to the platform (Fig. 1B). In addition, the platform is made in the form of a cryo aerogel, a solid substance filled with gas inside, exhibiting low density. Consequently, this photocatalyst-embedded elastomer-hydrogel was able to float on water (Fig. 1C).
The platform exhibits clear advantages in photocatalytic hydrogen evolution reactions: first, light attenuation by water is prevented, resulting in efficient conversion of solar energy. Second, the product, hydrogen gas, can be easily dispersed into air, avoiding the back-oxidation reaction and maintaining high reaction yields. Third, water can easily be supplied to the catalyst located within the elastomeric-hydrogel matrix due to its porosity. Lastly, the catalyst is stably immobilized in the matrix for long-term operation without leaching problems.
The researchers experimentally proved the superior hydrogen evolution performance of floating platforms, compared to conventional submerged platforms. In addition, the scalability of the platform, which is important for potential industrialization, is also shown in natural sunlight. It was confirmed that about 80 mL of hydrogen could be produced by a floatable photocatalytic platform using a single atom of copper and a titania catalyst with an area of 1 m22. Even after 2 weeks of operating in seawater containing various microorganisms and floating bodies, the evolutionary performance of the hydrogen platform was not compromised.
Prof. Kim stated, “The proposed platform can even produce hydrogen from solutions that dissolve household waste, such as polyethylene terephthalate bottles. Thus, this platform can be a solution for recycling waste, which contributes to an environmentally friendly society.”
In particular, this research presents a general platform for efficient photocatalysis that is not only limited to hydrogen production. It is possible to replace the catalytic components for a variety of desired applications, without changing the material properties of the floatable aerogel of the entire platform. This guarantees the broad application of the platform for other photocatalytic reactions, such as oxygen evolution reactions, hydrogen peroxide production, and the formation of various organic compounds.
“This study makes major advances in the field of photocatalysis and showcases the potential for green hydrogen production in the ocean with world-class performance. Distinctive material features, high performance and wide applicability in the field of photocatalysis our platform will undoubtedly open a new chapter in alternative energy,” said Prof. Hyeon.