Hydrogen for Energy Generated from Ethanol, Sunlight

(Energy.gov)

A team of researchers from Scotland, New Zealand, and Spain have developed a simpler and less expensive technology to generate hydrogen for energy. Their findings appear online in the journal Nature Chemistry (paid subscription required).

In this process, a solid photocatalyst is placed in a container with ethanol and exposed to ultraviolet light, part of the solar spectrum. The container has a titanium dioxide semiconductor in contact with sunlight that generates electrons captured by metallic gold nanoparticles. This titanium dioxide/gold compound reacts with the alcohol molecules in ethanol to produce hydrogen.

According to Jordi Llorca, one of the study’s authors and director of the Institute of Energy Technology at Universitat Politènica de Catalunya in Barcelona, the semiconductor’s structure and the contact with the nanoparticles are crucial features in the design of the photocatalyst. As a result, the amount of hydrogen and energy generated depends on the amount of photocatalyst used and the area exposed to solar radiation.

Until now, solar-generated hydrogen techniques used water, which is cheap and abundant, but require expensive catalytic materials and have not yet had good results. Instead of water, the researchers suggest using ethanol, a renewable and economical resource that can be obtained from agricultural and forest waste, not just food crops such as corn or sugar cane.

The photocatalyst is also much cheaper and simpler to use than the materials employed in techniques with water as it uses very small gold particles, ranging in size from 2 to 12 nanometers (1 nanometer equals 1 billionth of a meter). These nanoparticles capture the free electrons generated when the supporting material titanium oxide
comes into contact with sunlight.

Llorca plans to design reactors that can provide electricity to the home. One of the advantages of hydrogen compared with electricity is that it can be stored, while storing electric power requires large batteries. So far, Llorca says, researchers have generated up to 5 liters of hydrogen per kilogram of catalyst in one minute. If 9 kilograms of catalyst were put in an ethanol tank and exposed to sunlight, and the hydrogen generated were used to power a fuel cell, 3 kilowatts of electricity would be obtained, an amount similar to that which is used in a home.

Read more: New Process Devised For Efficient Hydrogen Production

*     *     *