Reviewed by Victoria SmithOct 24 2024
KAIST researchers have created an innovative hydrogen production system addressing green hydrogen generation challenges. The system uses a water-splitting process with an aqueous electrolyte, which is anticipated to prevent fire hazards and support stable hydrogen production. The study was published in the international journal Advanced Science.
Illustrations of a trifunctional graphene-sandwiched heterojunction-embedded layered lattice (G-SHELL) structure. Schematic representation of a) synthesis procedures of G-SHELL from a zeolitic imidazole framework, b) hollow core-layered shell structure with trifunctional sites for oxygen reduction evolution (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER), and c) heterojunctions, eterojunction-induced internal electric fields, and the corresponding band structure. Image Credit: Korea Advanced Institute of Science and Technology.
On October 22nd, KAIST (represented by President Kwang Hyung Lee) announced that a research team headed by Professor Jeung Ku Kang from the Department of Materials Science and Engineering has developed a self-sustaining hydrogen production system powered by a high-efficiency zinc-air battery.
Hydrogen is an essential raw material for producing high-value-added products. It is being recognized as a clean fuel with an energy density (142 MJ/kg) over three times that of conventional fossil fuels like gasoline and diesel. However, most current hydrogen production techniques contribute to environmental harm by releasing carbon dioxide.
Green hydrogen can be generated through water splitting using renewable energy sources like wind power and solar cells. However, these sources generate inconsistent power due to variations in weather and temperature, resulting in low water-splitting efficiency.
To address this, air batteries capable of providing sufficient voltage (greater than 1.23 V) for water splitting have received attention. However, achieving adequate capacity typically necessitates costly precious metal catalysts, and the catalyst's performance significantly deteriorates during extended charge and discharge cycles. Therefore, developing effective catalysts for water-splitting reactions (oxygen and hydrogen evolution) and materials that can stabilize repeated charge and discharge processes (oxygen reduction and evolution) in zinc-air battery electrodes is crucial.
Professor Kang's research team responded by suggesting a method for synthesizing a non-precious metal catalyst called G-SHELL. This material, effective for three catalytic reactions (oxygen reduction, oxygen evolution, and hydrogen evolution), is produced by growing nano-sized metal-organic frameworks on graphene oxide.
The team integrated the catalyst material into the air cathode of a zinc-air battery, demonstrating that it achieved approximately five times higher energy density (797 Wh/kg), strong power characteristics (275.8 mW/cm2), and long-term stability even under repeated charge and discharge conditions than conventional batteries.
The zinc-air battery, which functions with an aqueous electrolyte, is free from fire hazards. When combined with water electrolysis systems, this system is anticipated to be applicable as a next-generation energy storage device, providing an environmentally friendly approach to hydrogen production.
By developing a catalyst material with high activity and durability for three different electrochemical catalytic reactions at low temperatures using simple methods, the self-powered hydrogen production system we implemented based on zinc-air batteries presents a new breakthrough to overcome the current limitations of green hydrogen production.
Jeung Ku Kang, Professor, Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology
PhD Candidate Dong-Won Kim and Master's Student Jihoon Kim from the Department of Materials Science and Engineering at KAIST were co-first authors of this research.
This research received support from the Nano and Material Technology Development Program of the Ministry of Science and ICT and the National Research Foundation of Korea’s Future Technology Research Laboratory.
Journal Reference:
Kim, D. W., et al. (2024) Trifunctional Graphene‐Sandwiched Heterojunction‐Embedded Layered Lattice Electrocatalyst for High Performance in Zn‐Air Battery‐Driven Water Splitting. Advanced Science. doi.org/10.1002/advs.202408869.