A new study conducted by researchers at the University of Waterloo indicates that metal catalysts used for environmental sustainability degrade and become less effective.
This novel research – published in the journal Nature Catalysis – has highlighted that some tiny metal catalysts currently being studied for use in industrial-scaled environmental remediation efforts may be unstable during operation.
The scientists examined the structures of intricate catalysts known as ‘nanoscale electrocatalysts’ and discovered that they are not as stable as chemists once believed. When electricity flows through them during use, it is possible for the atoms to rearrange. In some cases, the team discovered, electrocatalysts entirely degrade.
Understanding nanoscale electrocatalyst degradation
Figuring out why the structure of metal catalysts rearrange and degrade is the first step to being able to utilise these nanoscale electrocatalysts in environmental remediation efforts such as removing atmospheric carbon dioxide and groundwater contaminants and transforming them into higher-value products such as fuels.
“Current electrocatalysts rely on complex nanoscale structures in order to optimise their efficiency,” explained Anna Klinkova, a professor in Waterloo’s Department of Chemistry. “What we found, however, is that the superior performance of these complex nanomaterials often come at a cost of their gradual structural degradation, as there is a trade-off between their effectiveness and stability.”
The researchers found that the rearrangement of atoms in the catalyst depended on the type of metal, structural shape, and the reaction conditions of the catalyst.
They detected two reasons for the rearrangements. Some small molecules can briefly attach to the surface of the catalyst and decrease the energy necessary for an atom to travel across the surface. In other cases, narrow areas within the catalyst concentrate the electron’s current, resulted in the metal atoms to displace via a process called electromigration.
Electromigration has been formerly detected in microelectronics, but this is the first time it has been connected to nanoscale catalysts.
These results determine a framework for evaluating structural stability and mapping the changing geometry of nanoscale catalysts, which is an essential step to designing better catalysts in the future.
“These structural effects could be used as one of the design rules in future catalyst development to maximise their stability,” Klinkova said. “You could also purposefully induce reconstruction to a different structure that becomes active as the reaction starts.”