Ulsan National Institute of Science and Technology (UNIST) announced on June 23 that its research team led by Professor Baek Jong-bum of the Energy and Chemical Engineering Department and a team led by Professor Bu Wenfei of the University of Nanjing have jointly developed a new high-efficiency catalyst consisting of zinc (Zn), nitrogen (N), and carbon (C) that can replace the platinum (Pt) catalyst used for fuel cell.
The researchers succeeded in finding active sites where the oxygen reduction reaction occurs in this catalyst. By designing and synthesizing catalysts based on active sites, the researchers expect to reach higher efficiency.
Existing catalyst studies were centered on synthesizing high-efficiency transition metal catalysts to replace expensive platinum. The studies examined to see if they could use other materials instead of platinum and can get high efficiency. However, there was a lack of research that focuses on finding specific sites, where optimized reactions occur, in newly synthesized catalysts.
The spectroscopic analysis equipment used by the researchers is the X-ray absorption analyzer. The device uses the fact that when an X-ray is applied, the electrons absorb the X-rays differently depending on the material. There are two types of analysis depending on the analysis area, and in the past, the EXAFS method, which only identifies the type of atomic bond, was used.
In addition to the EXAFS analysis, the XANES method was used in this study to identify the type of atoms as well as the bonding structure of atoms. As a result, the researchers found that the optimized catalytic site is a Zn-N₂ structure in which two nitrogen (N) atoms are bonded to one zinc atom. Experiments have also shown that the catalysts of this structure are superior to platinum in the rate of oxygen reduction.
Professor Baek said, "This research focuses on precise identification of the active site of the catalyst, deviating from previous studies that focused on development of catalyst performance. The catalyst efficiency can be dramatically improved because the catalyst can now be designed mainly by the active site structure.”
Dr. Feng Li of UNIST Department of Energy and Chemical Engineering, who led the study as a co-first author, said, "We have found that the Zn-N2 form, in which two nitrogen atoms are bonded to one zinc atom, is the ideal active structure for oxygen reduction catalysts. It will also help to find the active structure of other transition metal catalysts."
The study was published on June 13 in renowned international journal Nature Communications.