A new way to make industrial catalysts last longer, work faster and produce better results, is being developed by researchers at Cardiff University.
Their study, carried out with collaborators from Lehigh University in the USA, paired two common metals – gold and palladium – to see if they can cooperate during chemical reactions.
Their analysis, published in Nature Catalysis, reveals that when these metals are used together, they can interact electrically in a way that improves both efficiency and stability, offering a promising route to more sustainable chemical manufacturing.
Catalysts are essential for producing fuels, plastics and chemicals, but often degrade over time.
A major issue is that palladium – a widely used but expensive metal – can dissolve into the reaction liquid, reducing performance and increasing costs.
The research team set out to find a way to stop this loss without compromising performance.
We found that the gold actually protects the palladium. At a moderate pH, the palladium stops dissolving and becomes much more stable, reducing loss by close to 100%.
"Our previous findings also show that each of the metals boosts the others' performance, with gold handling one part of the reaction, while palladium handles the other," explains Dr Nouf Ali Alnahdi, who carried out the research as part of their PhD at Cardiff University.
"This teaming up means the overall reaction becomes faster and has important implications on stability too."
The researchers also tested the reaction at very high alkalinity - extreme pH – and found that despite the support of the gold, palladium still dissolves.
"Rather than becoming inactive, the dissolved palladium continued to influence the process through cooperation with the gold, speeding up the reaction all the same by over 4 times of the rate over just the gold," said co-author Dr Bohyeon Kim from Lehigh University in the USA.
This is important because it demonstrates that inactive dissolved metals can still play a significant role in the overall process, something that has gone unnoticed in these types of reactions until now.
The research builds on Cardiff University's groundbreaking research using gold to make better and more stable catalysts for chemical reactions. The team previously showed how gold and palladium, even when separated, can communicate through the reaction environment in a process termed Co-Operative Redox Enhancement (CORE).
This interaction changes the behaviour of each metal, allowing them to share the workload and perform separate parts of the reaction, ultimately boosting overall performance.
The study is part of a growing international project between Cardiff University and Lehigh University, where researchers are investigating CORE effects and their significance in a range of catalytic processes.
Dr Samuel Pattisson, a co-author of the study and postdoctoral researcher based at Cardiff University's School of Chemistry, added: "Our findings will facilitate the design of more efficient and stable materials for these important processes.
"Furthermore, we have uncovered a fundamentally new aspect of these processes whereby species that are otherwise completely inactive, still play a role when coupled with other components in the system across different phases."
This should lead to a reconsideration of practices such as 'hot filtration' experiments, which are commonly performed in heterogeneous catalysis to confirm the impact of leaching on a given process, but may be missing important information unless properly conducted.
The paper, 'The pH-dependant stabilisation and interphase coupling of Pd species during alcohol oxidation', is published in Nature Catalysis.
