This catalyst capability allowing stable hydrogen production from commercial diesel is expected to be applied in mobile fuel cell systems in the future hydrogen economy
On August 16, a joint research team led by Professors Joongmyeon Bae and Kang Taek Lee of KAIST's Department of Mechanical Engineering and Dr. Chan-Woo Lee of Korea Institute of Energy Research (KIER) announced the successful development of a highly active and durable reforming catalyst allowing hydrogen production from commercial diesel.
Fuel reforming is a hydrogen production technique that extracts hydrogen from hydrocarbons through catalytic reactions. Diesel, being a liquid fuel, has a high storage density for hydrogen and is easy to transport and store. There have therefore been continuous research efforts to apply hydrogel supply systems using diesel reformation in mobile fuel cells, such as for auxiliary power in heavy trucks or air-independent propulsion (AIP) systems in submarines.
However, diesel is a mixture of high hydrocarbons including long-chained paraffin, double-bonded olefin, and aromatic hydrocarbons with benzene groups, and it requires a highly active catalyst to effectively break them down. In addition, the catalyst must be extremely durable against caulking and sintering, as they are often the main causes of catalyst degradation. Such challenges have limited the use of diesel reformation technologies to date.
The joint research team successfully developed a highly active and durable diesel reforming catalyst through elution (a heat treatment method used to uniformly grow active metals retained in an oxide support as ions in the form of metal nanoparticles), forming alloy nanoparticles. The design was based on the fact that eluted nanoparticles strongly interact with the support, allowing a high degree of dispersion at high temperatures, and that producing an alloy from dissimilar metals can increase the performance of catalysts through a synergistic effect.
The research team introduced a solution combustion synthesis method to produce a multi-component catalyst with a trace amount of platinum (Pt) and ruthenium (Ru) penetrated into a ceria (CeO2) lattice, which is a structure commonly used as a support for catalysts in redox reactions. When exposed to a diesel reforming reaction environment, the catalyst induces Pt-Ru alloy nanoparticle formation upon Pt and Ru elution onto the support surface.
In addition to the catalyst analysis, the research team also succeeded in characterizing the behaviour of active metal elution and alloy formation from an energetic perspective using a density functional theory-based calculation. In a performance comparison test between the Pt-Ru alloy catalyst against existing single-metal catalysts, the reforming activity was shown to have improved, as it showed a 100% fuel conversion rate even at a low temperature (600oC, compared to the original 800oC). In a long-term durability test (800oC, 200 hours), the catalyst showed commercial stability by successfully producing hydrogen from commercial diesel without performance degradation.
The study was conducted by Ph.D. candidate Jaemyung Lee of KAIST's Department of Mechanical Engineering as the first author. Ph.D. candidate Changho Yeon of KIER, Dr. Jiwoo Oh of KAIST's Department of Mechanical Engineering, Dr. Gwangwoo Han of KIER, Ph.D. candidate Jeong Do Yoo of KAIST's Department of Mechanical Engineering, and Dr. Hyung Joong Yun of the Korea Basic Science Institute contributed as co-authors. Dr. Chan-Woo Lee of KIER and Professors Kang Taek Lee and Joongmyeon Bae of KAIST's Department of Mechanical Engineering contributed as corresponding authors. The research was published in the online version of Applied Catalysis B: Environmental (IF 24.319, JCR 0.93%) on June 17, under the title "Highly Active and Stable Catalyst with Exsolved PtRu Alloy Nanoparticles for Hydrogen Production via Commercial Diesel Reforming".
Professor Joongmyeon Bae said, "The fact that hydrogen can be stably produced from commercial diesel makes this a very meaningful achievement, and we look forward to this technology contributing to the active introduction of mobile fuel cell systems in the early hydrogen economy." He added, "Our approach to catalyst design may be applied not only to reforming reactions, but also in various other fields."
This research was supported by the National Research Foundation of Korea through funding from the Ministry of Science, ICT and Future Planning.
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Figure 1. Schematic diagram of high-performance diesel reforming catalyst with eluted platinum-ruthenium alloy nanoparticles and long-term durability verification experiment results for commercial diesel reforming reaction
