Busan National University Combines Graphene with Platinum-Nickel Nanoparticles... Achieves Up to 3 Times Efficiency

Next-Generation Catalyst Achieving Both Cost and Performance for Hydrogen Energy Innovation

Professor Lee Jung-woo's Team from the Department of Materials Science, Cover Paper in International Journal 'EcoMat'

Researchers at Pusan National University have developed a new catalyst for water electrolysis technology that extracts hydrogen from water and for use in hydrogen fuel cells.

The catalyst combines nano-sized particles of inexpensive nickel mixed with expensive platinum onto graphene, achieving up to three times the efficiency of existing catalysts while maintaining performance for over 10 hours, promising innovation in next-generation energy technology.

Pusan National University (President Choi Jae-won) announced on the 6th that Professor Lee Jung-woo's team from the Department of Materials Engineering successfully developed a catalyst for water electrolysis and hydrogen fuel cells with high current density by precisely controlling lattice contraction through compositional changes in platinum-based alloys and by forming heteroatomic bonds between nanoalloy particles and graphene.

According to the research team, water electrolysis is a technology that applies electrical energy to water to separate it into hydrogen and oxygen, with the advantage that carbon-based substances such as carbon dioxide (CO2) are not involved in the decomposition process.

Ongoing greenhouse effects and environmental issues caused by continuous fossil fuel use have increased interest in the development and utilization of alternative energy. In particular, hydrogen energy is attracting attention as a next-generation renewable energy source due to its high energy density per mass and the absence of carbon dioxide emissions during combustion.

Among these, water electrolysis and fuel cell technologies are being extensively researched as methods to produce and utilize hydrogen energy without using carbon-based materials. Currently, platinum (Pt) nanoparticles supported on amorphous carbon materials known as platinum/carbon black are used as commercial catalysts.

However, platinum/carbon black faces challenges in mass production and commercialization due to the high cost of platinum, its limited reserves, and the low long-term stability of carbon black.

In response, Professor Lee Jung-woo's team at Pusan National University conducted research to reduce the amount of platinum used while simultaneously improving the catalyst's activity and durability.

Nickel (Ni), one of the transition metals, costs about 1/2000 of platinum and is known to exhibit higher catalytic properties by creating synergy in hydrogen production and oxygen reduction when alloyed with platinum.

Graphene, one of the carbon allotropes, theoretically has a high specific surface area (surface area per unit mass of particles) and electron mobility, making it a promising support material to replace conventional carbon black. Furthermore, doping graphene with heteroatoms such as nitrogen can further enhance activity and durability.

The material developed by the research team was fabricated by a solution-phase process using microwaves, depositing uniform platinum-nickel nanoalloy particles of a few nanometers in size onto the surface of nitrogen-doped graphene.

This synthesis process uses polyol, an organic material containing hydroxyl groups (-OH), as a solvent. When microwaves are applied, frictional heat generated by the vibration of polyol reduces ionic metal precursors, inducing nucleation. This principle allows the production of uniform nanoscale materials within minutes, saving time and cost during processing.

The formed platinum-nickel nanoalloy clusters undergo lattice strain due to the atomic size difference between platinum and nickel. By adjusting the composition between platinum and nickel, the degree of lattice contraction can be controlled to understand catalytic activity trends and select the optimal composition.

Additionally, nitrogen doped on the graphene surface has high surface energy due to electronegativity differences with surrounding carbon atoms. The platinum-nickel nanoalloy clusters are synthesized via heterogeneous nucleation at these nitrogen sites and form chemical bonds. The electron transfer between bonded nitrogen and clusters and the high bonding energy result in higher catalytic activity and durability compared to carbon-cluster bonds.

The fabricated catalyst exhibited approximately three times higher specific activity and mass activity in oxygen reduction reactions compared to conventional platinum/carbon black materials, and about twice the specific and mass activity in hydrogen production reactions, due to the synergy between the optimized platinum-nickel alloy clusters and nitrogen-doped graphene.

The final implemented catalyst was applied to zinc-air secondary batteries, demonstrating more than twice the power density compared to commercial platinum and iridium catalysts. It maintained its initial activity even after more than 10 hours of charge-discharge cycles.

The research team collected hydrogen produced on the catalyst surface and observed volume changes over time, confirming stable hydrogen production as the amount of collected hydrogen increased linearly at regular intervals. Based on these results, the developed catalyst is expected to be applied in various fields such as hydrogen-powered vehicles, buses, and power generation systems as a next-generation energy production and utilization material.

Professor Lee Jung-woo of Pusan National University stated, “This research is significant in achieving higher catalytic activity than existing platinum catalysts by controlling lattice contraction through compositional changes in platinum-nickel alloys and forming nanoalloy cluster-nitrogen bonds via a rapid microwave heating synthesis process.” He added, “Because the catalyst fabrication process is fast and simple, and it reduces platinum usage while improving activity and durability, it is expected to have wide applications in the future.”

This research was conducted with doctoral student Cho Seung-geun and master's graduate Park Gil-ryeong from the Department of Materials Engineering at Pusan National University as first authors, and Professor Lee Jung-woo as corresponding author. It was carried out in collaboration with Professor Lee Deok-hyun's team from the Department of Electrical and New Materials Engineering at Andong National University and Dr. Kim Sun-yi's team at the Korea Institute of Energy Research. The study was supported by the Korea Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry and Energy's Energy Human Resources Development Program, as well as the Science and Technology Industrialization Promotion Agency and the Ministry of Science and ICT's Academic-Industrial Cooperation Platform Pilot Project.

The paper was published in the world-renowned scientific journal EcoMat on December 15, 2024, and was selected as a cover article in recognition of the excellence of the research.

(From left) Professor Lee Jung-woo, PhD candidate Cho Seung-geun, Master’s graduate Park Gil-ryeong.