Success in theoretical design of photocatalyst enabling mass production of hydrogen

Feb 06, 2013
Effect of the position of the Fermi level on the oxidation number of Cr and photocatalytic activity. (a) When the Fermi level is low, activity is reduced because unoccupied orbitals caused by high valence Cr capture photoexcited electrons. (b) The water splitting reaction is accelerated by eliminating unoccupied levels (i.e., stabilizing low oxidation number Cr) by elevating the Fermi level.

A research group headed by Dr. Naoto Umezawa, a Senior Researcher at the NIMS International Center for Materials Nanoarchitectonics (MANA), succeeded in theoretical design of a photocatalyst that enables hydrogen production by water splitting using sunlight.

Because the development of photocatalysts had been carried out based on the intuitions of researchers, systematic improvement of activity was difficult. Therefore, construction of design guidelines for promoting development with good visibility has been desired. Researchers around the world have attempted to select promising materials by conducting simulated experiments using computers and realize theory-led development, but few have been successful.

High expectations have been placed on strontium titanate (SrTiO3) as a photocatalyst. However, this compound cannot absorb visible light, which occupies a large part of the spectrum of sunlight. Therefore, we attempted to expand its visible by doping with such as Cr, etc. In recent years, much research has been done on co-doping of transition metal elements and other elements with the aim of stabilizing the oxidation number (valence) of the transition elements, but no clear guidelines exist for selection of the dopant.

In this research, we studied the optimum combination of dopants based on the electronic structures when Cr and various other elements are co-doped utilizing computational science. As a result, we predicted that the highest activity would occur when La, which has the capacity to form conduction electrons in SrTiO3, is co-doped with Cr. We also confirmed experimentally that this material exhibits in evolution of hydrogen from water under visible light irradiation, thus demonstrating the validity of the theory.

As hydrogen is expected to be an environment-friendly energy source, development of a technology that enables efficient production of hydrogen is awaited. This research demonstrated the effectiveness of theoretical design in the development of photocatalysts, thereby opening a new road toward the development of materials with higher activity. This approach is expected to make an important contribution to solving environmental and energy problems.

These results were published in the English scientific journal, Journal of Materials Chemistry A online on December 21, 2012.
See: pubs.rsc.org/en/content/articl… g/2013/TA/C2TA00450J

Explore further: Triplet threat from the sun

add to favorites email to friend print save as pdf

Related Stories

Improving performance of a solar fuel catalyst

Oct 04, 2012

(Phys.org)—Hydrogen gas that is created using solar energy to split water into hydrogen and oxygen has the potential to be a cost-effective fuel source if the efficiency of the catalysts used in the water-splitting ...

Water-splitting Photocatalyst Brought to Light

Jun 16, 2010

(PhysOrg.com) -- To produce "green" fuels, some scientists are looking for a little help from above. Sunlight is the key ingredient in photocatalytic water splitting, a process that breaks down water into ...

Recommended for you

Triplet threat from the sun

3 hours ago

The most obvious effects of too much sun exposure are cosmetic, like wrinkled and rough skin. Some damage, however, goes deeper—ultraviolet light can damage DNA and cause proteins in the body to break down ...

Towards controlled dislocations

Oct 20, 2014

Crystallographic defects or irregularities (known as dislocations) are often found within crystalline materials. Two main types of dislocation exist: edge and screw type. However, dislocations found in real ...

Chemists tackle battery overcharge problem

Oct 17, 2014

Research from the University of Kentucky Department of Chemistry will help batteries resist overcharging, improving the safety of electronics from cell phones to airplanes.

Surface properties command attention

Oct 17, 2014

Whether working on preventing corrosion for undersea oil fields and nuclear power plants, or for producing electricity from fuel cells or oxygen from electrolyzers for travel to Mars, associate professor ...

User comments : 0