Catalysts Research the NSRRC Collaborated on Published in Nature
2022/12/22
The National Synchrotron Radiation Research Center (NSRRC), funded by the National Science and Technology Council (NSTC), participated in a transnational research on catalysts, which was published in Nature on October 26th. This research team, consisted of Dr. Chih-Wen Pao of NSRRC, Prof. Jing-Yue Liu of Arizona State University, USA, and scientists from Stanford Synchrotron Radiation Lightsource (SSRL), USA. After five years, the team was the first to develop functional CeOx nanoglues; they are crystalline, ultrasmall, isolated on the SiO2 support, and characterized by a high number density of defect sites, making them ideal hosts for strongly bonded and isolated platinum (Pt) atoms, without sintering.
The team employed the “Quick-scanning X-ray Absorption Spectroscopy (Quick-EXAFS)” beamline of the Taiwan Photon Source (TPS) and beamlines at SSRL to analyze the local atomic structures around single metal atoms in the materials, and synthesized Pt single-atom catalysts of high efficiency and high stability. The catalytic efficiency has increased by nearly a hundred times.
At present, the chemical industry relies on catalysts for 90% of its processes. Catalysts are widely used in environmental protection facilities, such as flue gas denitrification in industrial plants, catalytic converters of a car's exhaust system, and in petroleum refining, for example. In recent years, extensive research on catalyst has been carried out in the field of green energy due to its increasing attention, such as water splitting for hydrogen production, nitrate reduction to ammonia, reduction of carbon dioxide, etc. The results of this study could help slow down global warming, as the international community aims for environmental sustainability and net-zero emission!
Many catalysts contain precious metals, and their atoms are identified as “active sites” in catalytic reactions. Previous studies found that only the outermost layer of metal atoms could play a role in catalytic reactions while others, not on the surface, were inactive. Since precious metals are rare and expensive, this inefficiency has become a challenge that scientists are eager to tackle.
Nowadays, precious metal “nanoparticles” are the main commercial production, but their catalytic efficiency and stability have its limitations. During the past decade, research on single-atom catalysts has flourished. Many scientists have studied single-atom structures and attempted to increase the number of single atoms per unit area, to maximize active sites, and hence improve catalytic performance and reduce the cost of precious metal catalysts.
However, sintering stops metal atoms from being dispersed on their supports stably. The research team successful developed a new method that allowed the nanoglues to anchor stably to high-surface-area supports as isolated “nanoglue islands.” The nanoglue islands then each host a single metal atom; each atom can move but remain confined to their respective nanoglue islands. This strategy not only makes every metal atom an individual active site but also enhances the reactivity. The catalytic efficiency of carbon monoxide oxidation reaction improved by nearly 100 times, and the cost is therefore lowered. This is definitely a huge step forward in single-atom catalysts.
The research team used XAFS at the TPS 44A beamline to conduct a coordination environment analysis in the three components their proposed strategy integrated into the catalyst: single metal atoms, nanoglues, and high-surface-area supports. The experimental technique of TPS 44A provides accurate measurement for structures of very tiny amount of atoms and molecules because of its ultra-high sensitivity at the atomic level and super-low detection limit (~one millionth).
Recently, the NSTC has launched the 2050 "Net-Zero Technology Champaign" in five net-zero fields, covering Sustainability & Advanced Energy, Low Carbon, Carbon Negative, Recycling, and Humanities & Social Sciences. Quick-EXAFS beamline at TPS is very suitable for studying the dynamics of fine structures at the atomic (10-10) level within millisecond (10-6). This technique is certainly a useful tool to study catalytic reactions, such as the dynamics of charge/discharge of lithium batteries as well as the process of absorption. It is also a powerful aid for achieving net zero emission by developing green energy materials, renewable energies, and low-carbon manufacturing.
