A team comprising scientists who specialize in structure materials at City University of Hong Kong (CityU) has developed a high-performance electrocatalyst based on an innovative concept originally for developing alloys. The new electrocatalyst can be produced at large scale and low cost, providing a new paradigm in a wide application of hydrogen production by electrochemical reaction in future.

The research was co-led by Professor Lu Jian, CityU’s Vice President (Research and Technology) and Chair Professor of Mechanical Engineering, and Professor Liu Chain-tsuan, University Distinguished Professor of the College of Engineering. The findings are published in the journal Advanced Materials.

Conceptual design of the multinary intermetallic electrocatalyst. This schematic diagram shows the dealloying process from a dual-phase structure to a dendritic-like structure. Source: CityU

Compared to other methods of hydrogen production, electrochemical water splitting is a relatively environmentally friendly process with promising potential in industrial applications. However, the most current developed electrocatalysts are noble-metal based, such as platinum and palladium. Their high costs and scarcity hinder the development and applications of this hydrogen production method.

Earlier, Professor Liu developed an innovative alloy design strategy for manufacturing high-entropy intermetallic compounds. This strategy overcomes the trade-off dilemma between strength and ductility in traditional metallic materials by introducing high density of nanoparticles of multi-component intermetallic compounds at the nano-scale. These findings were published in Science.

Since the high-entropy intermetallic compounds possess well-ordered atomic structures and chemical synergistic functions (thanks to its multi-components), both of which promote the electrocatalytic performance, the new alloy design strategy also provides insight for developing novel electrocatalysts.

Professor Liu’s team partnered with Prof Lu’s team, experts in noble metal research, and created a new high-entropy intermetallic (HEI) electrocatalyst by adopting the aforementioned alloy design strategy.

The new electrocatalyst mainly comprises iron, cobalt, nickel, aluminum and titanium. It also has a well-ordered atomic structure. Through a simple and one-step chemical method, the team produced a dendrite-like porous structure which greatly increased the surface area for electrochemical activities and hence significantly enhancing the electrochemical performance.

Using atomic-resolution scanning transmission electron microscopy (Cs-corrected) and 3D-atomic probe tomography in experiments, the team characterized the atomic structure of the HEI electrocatalyst. With further theoretical calculations, they proved that the synergistic effects and the well-ordered atomic structure effectively optimize the electronic structure, and hence promote the electrochemical water splitting process.

Because of its unique constituents and structure, this HEI catalyst performs excellent hydrogen evolution reaction in alkaline electrolyte.

Illustration of the hydrogen evolution reaction process. Source: CityU

Our unique strategy to produce HEI uncovers a new paradigm to develop novel electrocatalyst with superior reaction activities for splitting water and producing hydrogen.

—Professor Liu

The method that we used to prepare the HEI has already been widely employed in industrial production. Since we use the cheaper metals as raw materials, we believe this novel electrocatalyst will have promising application potential in industrial production of hydrogen.

—Professor Lu

Resources

• Jia, Z., Yang, T., Sun, L., Zhao, Y., Li, W., Luan, J., Lyu, F., Zhang, L.‐C., Kruzic, J. J., Kai, J.‐J., Huang, J. C., Lu, J., Liu, C. T. (2020) “A Novel Multinary Intermetallic as an Active Electrocatalyst for Hydrogen Evolution.” Adv. Mater. 32, 2000385. doi: 10.1002/adma.202000385