Scientists Use Sunlight to Produce Clean Hydrogen Fuel from Water

By Ham-Let

Osaka University researchers have developed an innovative form of photocatalyst* to produce hydrogen from water. The process is not only free of expensive metals, but absorbs a wider range of sunlight than ever before.

Water and fossil fuels contain large amounts of hydrogen —the most profuse element in the universe with huge potential to be the clean fuel of the future. However, unlocking molecular dihydrogen fuel from these sources involves a great deal of energy. To-date this has cast doubt over whether there is any economic future for hydrogen. However, converting H2O into hydrogen using solar energy could very well lead the way to clean and cheap hydrogen fuel. The downside is that its current capacity is limited given that the process depends on photocatalysts that comprise costly precious metals.

The situation might just be about to change. Lead author of the research team, who recently published their findings in the Journal of the American Chemical Society, said: “We were pleased to find a good amount of hydrogen produced from water using our new composite photocatalyst with graphitic carbon nitride and black phosphorous. But what we didn’t expect to find was that even when using low-energy light, in the near infrared, the photocatalyst continued to produce hydrogen.”

Like graphite — a crystalline allotrope of carbon, a native element mineral, a semi-metal, and a form of coal — graphitic carbon nitride (g-C3N4) forms in large sheets, however sheets of carbon nitride also have holes that can mix with hydrogen molecules. To-date, carbon nitride-based photocatalysts have depended on expensive precious metals to support them in producing hydrogen from water. The scientists have discovered that the metal can be substituted with a type of widely abundant and inexpensive black phosphorus (BP). They also revealed that their photocatalyst could effectively produce hydrogen from water via energy from diverse types of light — even low energy near infrared light can drive the creation of hydrogen!

Studying the operational photocatalyst in the picosecond time scale showed that robust interactions between the black phosphorous and carbon nitride in the composite, promoted the production of hydrogen. However, as soon as the two materials were tested separately, energy from the sunlight was quickly dispersed and no, or little, hydrogen was manufactured.

According to Majima, “the hydrogen economy faces a great many challenges, but our work demonstrates the potential for efficiently and cheaply producing hydrogen from water with a photocatalyst based on widely abundant elements. This is an important step toward making other hydrogen-based technologies economically and environmentally viable.”

*Photocatalyst is the acceleration of a photoreaction (a chemical reaction caused by absorption of ultraviolet, visible light, or infrared radiation) in the presence of a catalyst.

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