The limited reservoir of fossils fuels and the ever-increasing threats of climate change have encouraged researchers to develop alternative technologies to produce eco-friendly fuels. Green hydrogen generated from the electrolysis of water using renewable electricity is considered a next-generation renewable energy source for the future. But in reality, the overwhelming majority of hydrogen fuel is obtained from the refining of fossils fuels due to the high cost of electrolysis.
Currently, the efficiency of water electrolysis is limited and often requires high cell voltage due to the lack of efficient electrocatalysts for hydrogen evolution reactions. Noble metals such as platinum (Pt) are used as catalysts to improve hydrogen generation in both acidic/alkaline media. However, these noble metal catalysts are very expensive and show poor stability under long-term operation.
Single-atom catalysts have advantages over their nanomaterial-based counterparts, achieving up to 100 percent atom utilization, whereas only the surface atoms of nanoparticles are available for reaction. However, due to the simplicity of the single-metal-atom center, carrying out further modification of the catalysts to perform complex multistep reactions is rather difficult.
The simplest way to modify the single atoms is by turning them into single-atom dimers, which combine two different single atoms together. Tuning the active site of single-atom catalysts with dimers can improve the reaction kinetics thanks to the synergistic effect between two different atoms. However, while the synthesis and identification of the single-atom dimer structure have been known conceptually, its practical realization has been very difficult.
This problem was tackled by a research team led by Associate Director LEE Hyoyoung of the Center for Integrated Nanostructure Physics within the Institute for Basic Science (IBS) located at Sungkyunkwan University. The IBS research team successfully developed an atomically dispersed Ni-Co dimer structure stabilized on a nitrogen-doped carbon support, which was named NiCo-SAD-NC.
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