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New nanomaterial for energy conversion

Intensive research has focused on converting solar energy to provide clean chemical fuels like hydrogen as we spoke before. A promising solution comes from converting photon energy to hydrogen using a semiconductor material. One of the biggest difficulties in this process comes with the harvesting of photon energy across the wide solar spectrum (from ultraviolet (UV) to near-infrared (NIR) region) and simultaneously generate charge-carriers on the suitable energy levels for H+ reduction.

Many materials and technologies have long been studied as photocatalyst for solar-driven water splitting. It appears difficult to find a suitable candidate compatible with the whole solar spectrum. However, some solutions were presented using a variety of techniques, including heavily doping, integrating narrow band gap semiconductors, and decorating with noble metals and co-catalysts to increase the absorption range to include visible or NIR.

A recent study from NanoScience Technology Center in Florida reported nanomaterial heterostructures could be highly efficient for photocatalytic H2 generation. The team led by Y. Yang used laminated molybdenum disulfide (MoS2) in conjunction with TiO2 nanocavity arrays. This complex structure obtained by a carefully controlled anodization offered a broad spectral response ranging from ultraviolet-visible (UV-vis) to near-infrared (NIR) wavelengths. They demonstrated that the spatially uniform heterostructure, correlated with plasmon-resonance was very efficient in harvesting solar energy and for photocatalytic H2 production.

Schematic illustration of the fabrication process of the heterostructure nanomaterial.

”We've opened a new window to splitting real water, not just purified water in a lab. This really works well in seawater. […] We can absorb much more solar energy from the light than the conventional material. Eventually, if it is commercialized, it would be good for Florida's economy. We have a lot of seawater around Florida and a lot of really good sunshine."

Y. Yang, NanoScience Technology Center, Florida

In many situations, producing a chemical fuel from solar energy is a better solution than producing electricity from solar panels. That electricity must be used or stored in batteries, which degrade, while hydrogen gas is easily stored and transported. As an innovative exploration, this study demonstrates that the photocatalytic process using earth-abundant materials can be enhanced with plasmonic effects, which may serve as an excellent catalytic agent for solar energy conversion to chemical fuels. This way, fabricating the catalyst is relatively easy and inexpensive.

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