Ion beam technology creates advanced catalysts for hydrogen energy production

Electrochemical water splitting is a promising technique for producing clean hydrogen, but is hindered by slow reaction kinetics from four-electron transfer steps. Efficiency can be enhanced with catalysts such as high-entropy oxide (HEO) nanomaterials, which have rich atomic components, highly exposed active surfaces, and controlled physicochemical properties. Their fabrication, however, is challenging.

Wu et al. demonstrated a general method to prepare HEO nanoparticles by low-energy-recoil ion implantation, with controllability and precision of ion beam technology enabling nanoscale tuning.

“Ion beam technology is a novel and physical method to modify and fabricate materials, and now we can extend the application of ion beam technology to the preparation of HEO nanoparticle catalysts,” said author Feng Ren.

In the team’s experiments, high-energy ions were used to irradiate the free-standing HEO film, low-energy metal atoms in the film were knocked out, and low-energy-recoil ions were implanted into the substrate. By controlling the irradiation fluence of ions and subsequent annealing, the size and load of HEO nanoparticles could be tailored accurately.

“The traditional physical and chemical methods struggle to form small size HEO nanoparticles with different elemental composition,” said author Shixin Wu. “Our proposed method of low-energy recoil implantation achieved precise physical size regulation. Moreover, the HEO nanoparticles can firmly anchor onto the surface of the substrate, providing good stability as catalysts.”

The team showcased the method’s generalizability by synthesizing binary and medium-entropy oxide nanoparticles, and HEO nanoparticles with ideal catalytic properties for the oxygen evolution reaction.

“In principle, HEO nanoparticles with any elemental composition can be obtained through this method by changing the free-standing film,” said Ren.

Source: “A general method to synthesize high-entropy oxide nanoparticles by low-energy-recoil ion implantation for efficient oxygen evolution reaction,” by Shixin Wu, Huizhou Zhong, Shuangfeng Jia, Derun Li, Tao Jiang, Yichao Liu, Hengyi Wu, Guangxu Cai, and Feng Ren, Applied Physics Reviews (2023). The article can be accessed at https://doi.org/10.1063/5.0155397 .