Improving performance of a solar fuel catalyst

October 4, 2012
False-color scanning electron micrographs of cross-sectioned hematite films grown by sputter deposition and then annealed at two different temperatures.  The physical structure and the tin dopant atom distributions in the hematite films differ depending on the annealing temperature.  Hematite annealed at higher temperatures has better catalytic performance for splitting water. 

(—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 process can be improved. By controlling the placement of key additives (dopant atoms) in an iron oxide catalyst, researchers from the NIST Center for Nanoscale Science and Technology have found that the final location of the dopants and the temperature at which they are incorporated into the catalyst crystal lattice determine overall catalytic performance in splitting water.

The iron oxide hematite is a promising catalyst for water splitting because it is stable in water and absorbs a large portion of the . It is also abundant in the earth's crust, making it inexpensive. Unfortunately, pure hematite has only modest catalytic activity, falling well short of its predicted theoretical maximum efficiency. Incorporating dopants such as tin atoms into hematite's lattice improves performance, but it is a challenge to accurately measure the dopant concentration, making it difficult to understand and optimize their effects on catalyst performance.

Using thin films of hematite doped with tin, the researchers produced highly active samples that enabled them to measure and characterize the spatial distribution of dopants in the material and their role in catalysis. The researchers determined that as a result of the sample preparation protocol they followed, a dopant gradient extends from the interface with the dopant source to the catalyst surface, where the measured concentration is low compared with previous estimates from similarly prepared samples.

Contrary to prior results, they found that only a small dopant concentration is needed to improve catalytic activity. The researchers believe this study creates a path for improving the rational design of inexpensive catalysts for using solar energy.

Explore further: Efficient Catalysts for Making Oxygen for 'Artificial Photosynthesis'

More information: Effect of tin doping on α-Fe2O3 photoanodes for water splitting, C. D. Bohn, A. K. Agrawal, E. C. Walter, M. D. Vaudin, A. A. Herzing, P. M. Haney, A. A. Talin, and V. A. Szalai, The Journal of Physical Chemistry C 116, 15290–15296 (2012).

Related Stories

Cheap hydrogen fuel from seawater may be a step closer

April 29, 2010

( -- A new catalyst has been developed to generate hydrogen from water cheaply, but the research was originally intended to make molecules that behaved like magnets. Hydrogen is a clean power source currently ...

Highly efficient oxygen catalyst found

October 28, 2011

A team of researchers at MIT has found one of the most effective catalysts ever discovered for splitting oxygen atoms from water molecules — a key reaction for advanced energy-storage systems, including electrolyzers, ...

Recommended for you

Organic semiconductors get weird at the edge

October 6, 2015

As the push for tinier and faster electronics continues, a new finding by scientists at the University of British Columbia (UBC) and Monash University could help inform the design of the next generation of cheaper, more efficient ...

New polymer creates safer fuels

October 1, 2015

Before embarking on a transcontinental journey, jet airplanes fill up with tens of thousands of gallons of fuel. In the event of a crash, such large quantities of fuel increase the severity of an explosion upon impact. Researchers ...

Researchers print inside gels to create unique shapes

September 30, 2015

(—A team of researchers at the University of Florida has taken the technique of printing objects inside of a gel a step further by using a highly shear-rate sensitive gel. In their paper published in the journal ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.