Platinum-based heterogeneous catalysts are critical to many important commercial chemical process... more Platinum-based heterogeneous catalysts are critical to many important commercial chemical processes, but their efficiency is extremely low on a per metal atom basis, because only the surface active-site atoms are used. Catalysts with single-atom dispersions are thus highly desirable to maximize atom efficiency, but making them is challenging. Here we report the synthesis of a single-atom catalyst that consists of only isolated single Pt atoms anchored to the surfaces of iron oxide nanocrystallites. This single-atom catalyst has extremely high atom efficiency and shows excellent stability and high activity for both CO oxidation and preferential oxidation of CO in H2. Density functional theory calculations show that the high catalytic activity correlates with the partially vacant 5d orbitals of the positively charged, high-valent Pt atoms, which help to reduce both the CO adsorption energy and the activation barriers for CO oxidation.
International Journal of Pediatric Otorhinolaryngology, 2004
NixZn1−xFe2O4 (0.2≤x≤0.7) thin films with various compositions are prepared by alternative sputte... more NixZn1−xFe2O4 (0.2≤x≤0.7) thin films with various compositions are prepared by alternative sputtering technology from the two targets with the composition NiFe2O4 and ZnFe2O4. The films are deposited on (1 1 1) Si substrates directly and buffered with ZnFe2O4 underlayer, respectively, at room temperature and then annealed in air at 850 °C. For unbuffered films with the increasing of Zn content, the saturation magnetization Ms increases firstly and then decreases when x=0.40 the Ms reaches the maximum value about 400 emu/cc, while the coercivity Hc decreases monotonously. The films grown on substrates with ZnFe2O4 underlayer exhibit better magnetic properties than those deposited on directly Si substrates which indicates the importance of lattice match and structural similarity between the film and the underlayer.
The interaction of cobalt atoms with silicon (1 1 1) surface has been investigated by means of sc... more The interaction of cobalt atoms with silicon (1 1 1) surface has been investigated by means of scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). Besides the Co silicide islands, we have successfully distinguished two inequivalent Co-induced 13×13 reconstructions on Si(1 1 1) surface. Our high-resolution STM images provide some structural properties of the two different 13×13 derived phases. Both of the two phases seem to form islands with single domain. The new findings will help us to understand the early stage of Co silicide formations.
Platinum-based heterogeneous catalysts are critical to many important commercial chemical process... more Platinum-based heterogeneous catalysts are critical to many important commercial chemical processes, but their efficiency is extremely low on a per metal atom basis, because only the surface active-site atoms are used. Catalysts with single-atom dispersions are thus highly desirable to maximize atom efficiency, but making them is challenging. Here we report the synthesis of a single-atom catalyst that consists of only isolated single Pt atoms anchored to the surfaces of iron oxide nanocrystallites. This single-atom catalyst has extremely high atom efficiency and shows excellent stability and high activity for both CO oxidation and preferential oxidation of CO in H2. Density functional theory calculations show that the high catalytic activity correlates with the partially vacant 5d orbitals of the positively charged, high-valent Pt atoms, which help to reduce both the CO adsorption energy and the activation barriers for CO oxidation.
International Journal of Pediatric Otorhinolaryngology, 2004
NixZn1−xFe2O4 (0.2≤x≤0.7) thin films with various compositions are prepared by alternative sputte... more NixZn1−xFe2O4 (0.2≤x≤0.7) thin films with various compositions are prepared by alternative sputtering technology from the two targets with the composition NiFe2O4 and ZnFe2O4. The films are deposited on (1 1 1) Si substrates directly and buffered with ZnFe2O4 underlayer, respectively, at room temperature and then annealed in air at 850 °C. For unbuffered films with the increasing of Zn content, the saturation magnetization Ms increases firstly and then decreases when x=0.40 the Ms reaches the maximum value about 400 emu/cc, while the coercivity Hc decreases monotonously. The films grown on substrates with ZnFe2O4 underlayer exhibit better magnetic properties than those deposited on directly Si substrates which indicates the importance of lattice match and structural similarity between the film and the underlayer.
The interaction of cobalt atoms with silicon (1 1 1) surface has been investigated by means of sc... more The interaction of cobalt atoms with silicon (1 1 1) surface has been investigated by means of scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). Besides the Co silicide islands, we have successfully distinguished two inequivalent Co-induced 13×13 reconstructions on Si(1 1 1) surface. Our high-resolution STM images provide some structural properties of the two different 13×13 derived phases. Both of the two phases seem to form islands with single domain. The new findings will help us to understand the early stage of Co silicide formations.
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Papers by Yitao Cui