The use of precious metals as catalysts may be significantly reduced with the use of a new nanoparticle catalyst, a new research found.
Catalysts are vital in many technologies because they hasten chemical reactions without being consumed by the process, but their composition of precious metals such as palladium or platinum makes them quite expensive.
Massachusetts Institute of Technology (MIT) researchers may have found a solution on how to create a catalytic reaction by using only 10 percent of precious metals.
Proven Stability And Longevity
The researchers used a thin coating of a precious metal to cover a small particle made of transition metal carbide, which is inexpensive and more common. They were able to make the coating stay glued to the ceramic material, suggesting that coated particles are even better than existing catalysts made entirely of precious metals. The method has actually been a subject of several research but none of them were able to make the coating adhere to the underlying metal.
With this, the nanoparticle catalysts have longer lifespan and the ability to resist unwanted phenomena commonly encountered with the use of conventional metal catalysts.
MIT's Department of Chemical Engineering associate professor Yuriy Román-Leshkov said that while some early researchers were able to successfully use cobalt and nickel, the stability of these particles is not reliable. They also result in clustering with the precious metal shell. With carbides, rusting, alloying and clustering do not occur and that makes them the best metals to use as core material.
Researchers did not think that they would achieve success with their study primarily because noble metals have difficulty bonding with other materials. Additionally, fashioning transition metal carbides into nanoparticles is also extremely hard - forming a metal lattice with the use of high temperatures results in clumping and surface contamination.
MIT doctoral student and co-researcher Sean Hunt explained that they were able to achieve the adherence by coating the shell and carbide with a silica template.
Nanoparticle Catalysts Fueling The Future
"This keeps them close together during the heat treatment, making them self-assemble into core-shell structures, conveniently solving both challenges at the same time," said Hunt as he spoke of the breakthrough technology used. The template would then be treated away using an acid.
Solving the challenges paved the way for more important benefits. The inability of precious metals to adhere to other materials meant that complex catalytic designs can be created using a variety of noble metals in the shell and several other inexpensive carbide cores.
To prove this, a nanoparticle made with ruthenium and platinum shell covering for a carbide core composed of titanium and tungsten was used in 10,000 electrochemical cycles in direct methanol fuel cell applications. It was found to still perform significantly better than traditional nanoparticles.
Another useful application of the method is by preventing precious metal catalysts to undergo carbon monoxide surface poisoning as the core-shell catalysts could withstand as much as 1,000 parts per million of carbon monoxide.
The core-shell structure developed by the researchers also proved that it can tolerate different reaction types, while still maintaining its properties.
While the method still needs further studies to become available commercially, the principle already shows benefits for fuel cell applications.
Columbia University chemical engineering professor Jingguang Chen, who was not part of the study, said the discovery is very important in reducing the use of precious metals and shows great promise for use commercially.
Tech Times once reported that researchers were looking for alternative catalysts that can be used in fuel cells. James Gerken, who does extensive research about hydrogen fuel cells shared: "The specific catalysts that we used have some drawbacks for commercial applications, so the next step will be to find catalysts with better long-term stability and even higher efficiency."
Could these nanoparticle catalysts be the answer?
The study was published in Science on May 20.
