It utilizes a high-performance, durable catalyst for three essential reactions at low temperatures with straightforward implementation.
Researchers have created a new hydrogen production system that addresses the limitations of current green hydrogen methods.
A Korea Advanced Institute of Science and Technology (KAIST) team’s system uses a water-splitting process with a water-soluble electrolyte to ensure stable hydrogen production while reducing the risk of fire.
The group created a system that produces hydrogen on its own using a high-performance zinc-air battery.
The zinc-air battery-based hydrogen system uses a high-activity, long-lasting catalyst for three key reactions at low temperatures and with simple implementation.
Researchers claim the new catalyst will be a “new breakthrough that can overcome the limitations of current green hydrogen production,” said Jeung Ku Kang, a professor in the Department of Materials Science and Engineering at KAIST.
Hydrogen efficiency challenge
Hydrogen (H₂) is gaining recognition as a clean fuel due to its high energy density of 142 MJ/kg—three times greater than that of fossil fuels like gasoline and diesel. However, conventional hydrogen production methods result in significant carbon dioxide (CO₂) emissions.
It is more environmentally good to produce green hydrogen through water splitting using renewable energy sources like solar and wind power, although these sources frequently have efficiency problems because of temperature and weather variations.
Air cells that can provide a voltage of 1.23 V or more for water splitting are being investigated as other power sources to overcome this difficulty. To get the necessary capacity, these air cells must use precious metal catalysts, and prolonged charging and discharging quickly degrades the catalyst materials’ efficacy.
Illustrations of the G-SHELL structure include a) synthesis from a zeolitic imidazole framework, b) hollow core-shell with trifunctional sites for ORR, OER, HER, and c) heterojunctions with induced electric fields and band structure.
The team claims that the constraint emphasizes the need for more reliable and affordable alternatives in the pursuit of sustainable and effective green hydrogen production.
“Therefore, it is essential to develop a catalyst that is effective for water splitting reactions (oxygen generation, hydrogen generation) and a stable material for repeated charge and discharge reactions (oxygen reduction, oxygen generation) of zinc-air battery electrode.
Efficient catalyst innovation
In their new work, KAIST researchers developed a new non-precious metal catalyst material (G-SHELL) using a graphene-sandwiched, layered structure.
The basis of G-SHELL is a zeolitic imidazole framework (ZIF) atop a graphene oxide (GO) surface. It has a hollow core-shell structure with distinct catalytic layers: a core of cobalt(II, III) sulfide (Co₃S₄) that promotes oxygen evolution (OER) and shell layers of molybdenum disulfide (MoS₂) that promote hydrogen evolution (HER) and oxygen reduction (ORR) processes.
The 3D hollow form accelerates ion transport, while conductive graphene layers between the core and shell function as electron channels. Advanced imaging and analysis confirm its structure and internal electric fields enhance electron transport for quicker reactions.
Lastly, G-SHELL uses a rechargeable zinc-air battery (ZAB) to power a water-splitting system. It exhibits great efficiency for multiple reactions, turning air into hydroxides during discharge and producing oxygen during charge.
The research team verified that the air battery’s designed catalyst has an energy density of 797 Wh/kg, which is five times greater than that of current batteries. Under repeated charging, it maintains a steady long-term operation with a high output of 275.8 mW/cm².
The zinc-air battery is regarded as an environmentally favorable hydrogen generation method because it uses a water-soluble electrolyte and is fireproof. According to researchers, it can be used as a next-generation energy storage device in conjunction with a water electrolysis system.