UC Davis researchers invent a new method for maintaining the efficiency of platinum catalysts
By EKATERINA MEDVEDEVA — science@theaggie.org
If you have taken an introductory chemistry course before, then you have probably heard of catalysts — compounds that lower the amount of activation energy needed for a reaction to occur by offering an alternative pathway. As a result, the process is faster and more energy-efficient.
Catalysts are essential in a diverse range of industries that involve working with chemical reactions: petrochemicals, pharmaceuticals, food production, energy — you name it.
“Approximately 90% of all commercially produced chemical products rely on [catalysts],” an article released by Topsoe, a large Danish company specializing in catalysts and other technologies aimed at decarbonization, reads.
So, the more efficient the catalysts are at their job, the better it is for everybody. Recently, a UC Davis research group led by Professor Bruce Gates in the Department of Chemical Engineering conducted a study that resulted in the development of a nanoscale confinement strategy for platinum (Pt) cluster catalysts.
The study is co-authored by a postdoctoral UC Davis fellow, Yizhen Chen, and Jiankang Zhao of the School of Materials and Energy at the University of Electronic Science and Technology of China, Chengdu, People’s Republic of China. This research significantly improved the efficiency of the platinum cluster catalysts under harsh conditions of reducing hydrogenic reactions “at temperatures of ≤600 °C and atmospheric pressure.”
“Most catalysts that are used to make industrial products are solids and a lot of them are used at high temperatures, so they have to have ‘stability,’” Gates said. “Usually, 99% plus of [the catalyst] is [composed of] material that’s not very expensive but has a lot of internal surface area due to being porous, like Swiss cheese. These tiny pores provide platforms or sites for the expensive component in a catalyst, [one type of which] are noble metals [such as] platinum, palladium and rhodium. Platinum costs about $1,000 per ounce, palladium costs about the same and rhodium costs much more. So, the catalyst design needs to be getting the biggest bang for the buck from the expensive components.”
The biggest problem with noble metal catalysts that the team addressed is that they are prone to moving around on the porous support and sintering, or agglomerating, into larger particles under practical reaction conditions, which may involve temperatures of up to 800°C. This results in a reduction of their surface area for interacting with reactants, which, in turn, causes a drop in efficiency of the reaction.
“We devised a confinement strategy that anchors each [atom-precise low-nuclearity Pt] cluster onto an individual cerium oxide (CeOx) nanoisland, forming isolated nanoreactors that are highly dispersed on a high-surface-area porous silica (SiO2) support,” the research brief reads. “This design prevents cluster migration and aggregation under harsh reducing conditions.”
The experiments for the different parts of the study, such as determining the structure and function of the new catalysts as well as testing them under hydrogenic catalysis, were done in numerous places, including the laboratories of Bainer Hall at UC Davis and the Stanford Linear Accelerator Center (SLAC) laboratory.
“The key experiments were done by [our] colleagues in China,” Gates said. “[This study] is a collaborative work involving [a lot of] people and many different institutions. That’s how [a lot of] science gets done these days — it’s networking, it’s teamwork, it’s figuring out who can bring what skills to the party and then trying to coordinate the work so that everybody is on the same page, communicating effectively and collecting the information needed to move the science forward.”
The study continues to be developed, primarily by researchers in China who have been involved in this groundwork.
“We have been working with catalysts that are similar to the ones described in the publication, but modified in ways that change their properties,” Gates said. “We’d like to think that the work in that publication and in the publication that preceded it in the journal Nature opened some valuable new territory. Now I think it’s fair to say that the follow-up work is consolidating and defining the new territory better.”
Written by: Ekaterina Medvedeva — science@theaggie.org
