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Japan: Hydrogen Economy Efficient Splitting of Water for Hydrogen Production

| Editor: Alexander Stark

Researchers at Osaka University have developed a new catalytic system for efficiently splitting water and making hydrogen with energy from normal sunlight. Their study was recently reported in Angewandte Chemie International Edition.

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Photocatalytic overall pure-water splitting using the 2D heterostructures of BP/BiVO4 without any sacrificial agents under visible light irradiation.
Photocatalytic overall pure-water splitting using the 2D heterostructures of BP/BiVO4 without any sacrificial agents under visible light irradiation.
(Source: University of Osaka)

Osaka/Japan — Hydrogen as a fuel source, rather than hydrocarbons like oil and coal, offers many benefits. Burning hydrogen produces harmless water with the potential to eliminate carbon dioxide emissions and their environmental burden. In pursuit of technologies that could lead to a breakthrough in achieving a hydrogen economy, a key issue is making hydrogen cheaply.

Using catalysts to split water is the ideal way to generate hydrogen, but doing so usually requires an energy input from other chemicals, electricity, or a portion of sunlight which has high enough energy.

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Until now, it has not been possible to use visible light for photocatalysis. The new approach developed by the Japanese scientists combines nanostructured black phosphorus for water reduction to hydrogen and bismuth vanadate for water oxidation to oxygen. According to Mingshan Zhu, this allowed them to use a of a wide range of the solar spectrum to produce hydrogen and oxygen with unprecedented efficiency.

Black phosphorus has a flat, two-dimensional structure similar to that of graphene and strongly absorbs light across the whole of the visible spectrum. The researchers combined the black phosphorus with bismuth vanadate, which is a well-known water oxidation catalyst.

In the same way that plants shuttle electrons between different structures in natural photosynthesis to split water and make oxygen, the two components of this new catalyst could rapidly transfer electrons excited by sunlight. The amounts of the two components was also optimized in the catalyst, leading to production of hydrogen and oxygen gases in an ideal 2:1 ratio.

Coauthor Tetsuro Majima commented that the realization of hydrogen production powered by sunlight was the foundation of a hydrogen-oriented society, adding that their contribution would overcome a significant hurdle.

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