In brief

The ultrafast heating method generates single-atom catalysts with fewer impurities, enhancing their ability to accelerate reactions.

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Ultrafast heating sparks high-performing catalysts

2 Sep 2022

Researchers developed a new technique for manufacturing powerful and versatile synthetic catalysts.

It usually only takes a spark to get a fire going. In the case of chemical reactions for manufacturing processes, this spark is a catalyst—a substance added to galvanise reaction speeds to boost efficiency. Single-atom catalysts, or SACs, are a relatively new class of synthetic materials that are leading the pack: they are incredibly potent and exhibit unparalleled breadth, accelerating a wide range of chemical reactions.

SACs get their power from a highly reactive metal core that is supported by a molecular mesh of non-metal dopants. Getting the balance right, however, is a challenge: current manufacturing techniques often use an excess of dopants which causes impurities to impinge on the metallic active site, thereby weakening SACs’ performance.

In collaboration with Yujie Xiong from the University of Science and Technology of China (USTC), A*STAR researchers Xian Jun Loh and Enyi Ye, from the Institute of Materials Research and Engineering (IMRE) hypothesised that a ‘heat shock method’ commonly used in building synthetic materials could also serve as a viable solution for generating better SACs. The researchers tested their theory using carbon-supported nickel SACs as a model.

The researchers developed a novel joule heating strategy for creating SACs. This ultrafast heating method causes the temperature to surge over 2,700°C in just a few milliseconds, limiting opportunities for dopant impurities to form on SACs. In turn, several trial manufacturing runs were performed using different ratios of SAC building blocks to determine the optimal conditions for high-performance SACs. The catalytic activity of these test SACs was then assessed using carbon dioxide reduction (CO2RR), a reaction used in the fuel industry.

The team found that the heat shock method exceeded expectations. Traditional SACs typically achieve selectivity rates of around 90 percent within a small reaction voltage range. The next-generation SACs developed by the team surpassed 92 percent selectivity across a higher voltage window.

“We are breaking the voltage range limitation of high CO selectivity catalysts,” said Ye, adding that this enables high-efficiency reactions even with voltage fluctuations during manufacturing.

As part of their study, the researchers demonstrated the versatility of their new method, generating a library of other metal-based SACs including copper, zinc and iron. Ye notes that this work provides a blueprint for the next wave of high-performance SACs by mapping molecular structures with catalytic properties.

“It opens a new way of designing high-performance SACs,” said Ye. “For example, researchers could apply our method to introduce non-metal dopants into their SACs efficiently.”

The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering (IMRE).

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Xi, D., Li, J., Low, J., Mao, K., Long, R. et al. Limiting the Uncoordinated N Species in M–Nx Single-Atom Catalysts toward Electrocatalytic CO2 Reduction in Broad Voltage Range, Advanced Materials 2021, 2104090. | article

About the Researchers

Xian Jun Loh received his PhD in 2009 from the National University of Singapore and joined A*STAR in 2013. A polymer chemist with 20 years of experience working with biomaterials, Loh is currently Executive Director at the Institute of Materials Research and Engineering (IMRE). His research interests lie in the design of supramolecular and stimuli-responsive polymers and hydrogels for biomedical and personal care applications.
Enyi Ye is currently the Deputy Department Head of Advanced Biomaterials (ABM) and Group Leader of Nano+ at IMRE, A*STAR. He was trained in Chemical Physics at the University of Science and Technology of China and obtained his PhD in Chemistry from the National University of Singapore. His research interests focus on the development of multifunctional inorganic/polymeric materials for applications in biomedicine, cosmetics, personal care and catalysis.

This article was made for A*STAR Research by Wildtype Media Group