Diagram of the reaction that uses platinum as a catalyst to turn carbon monoxide and water into carbon dioxide and hydrogen.
Research by the U.S. Department of Energy’s Brookhaven National Laboratory (BNL) and Stony Brook University (SBU) in New York, among others, has uncovered the fundamental use of platinum within the catalyst used to produce hydrogen, helping to reduce costs by reducing the amount of platinum used within the catalyst.
One method of producing hydrogen is to take carbon monoxide and water, and turn them into carbon dioxide and hydrogen in the presence of a catalyst. This is an important step needed to produce and purify hydrogen for a variety of uses such as clean energy car batteries and the production of hydrocarbons. Platinum is an important component of the catalyst.
Platinum is costly. This new study identifies the key to the process of catalyst action that will reduce the amount of platinum used.
Part of the difficulty is that the catalyst has a very complex structure,” says Yuanyuan Li, the study’s principal investigator. The catalyst consists of platinum nanoparticles (platinum atoms clustered in a pile) attached to the surface of cerium oxide. Some of the platinum atoms are on the surface of the nanoparticles and some are in the core; some are on the contact surface between the nanoparticles and the cerium and some are on the outer boundary of the contact surface. The differences in where the atoms are located and the way they are distributed on the surface result in some atoms being exposed and others not, both of which affect how the platinum atoms interact with the gas molecules.”
Previous experiments have produced conflicting results as to whether chemical reactions occur on nanoparticles or individual platinum atoms, and whether the reaction sites carry a positive or negative charge.
“We wanted to solve these problems. To find the site of the reaction and understand the reaction process, it would be desirable to study this catalyst at the atomic level.”
The researchers used a variety of techniques to observe the reaction process at the microscopic level. “We found that only the platinum atoms at the periphery of the nanoparticle-cerium junction provide catalytic activity. The dynamic nature of these reaction sites drives carbon monoxide to gain oxygen from water to become carbon dioxide and water molecules to lose oxygen to become hydrogen.”
Yuan-Yuan Li says, “We took it for granted that all the platinum atoms located at the contact surfaces were involved, but they were not. We don’t need all the platinum atoms, just the ones that are involved. This helps us to remove unnecessary atoms and reduce the cost of the catalyst. We think this mechanism holds true for other systems that use catalysts for reactions.”
The study was published Feb. 10 in the journal Nature Communications.
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