Identifying the active site of oxide-supported metal catalysts and revealing the intrinsic synergistic mechanism between metal and oxide support remain a large challenge.Herein,we report the identification and separat...Identifying the active site of oxide-supported metal catalysts and revealing the intrinsic synergistic mechanism between metal and oxide support remain a large challenge.Herein,we report the identification and separation of the Pt-O-Ti interface and TiO_(2) surface in Pt-TiO_(2)-based catalysts by depositing different thickness of TiO_(2) shell with∼0.4-nm micropores onto the surface of Pt/TiO_(2) catalyst through atomic layer deposition(ALD).In the oxidation of 3,3′,5,5′-tetramethylbenzidine(TMB)by hydrogen peroxide(H_(2)O_(2))process,the TiO_(2) microporous shells can prevent the contact between TMB and embedded Pt clusters,but not delay the diffusion of H_(2)O_(2).The heterolysis of H_(2)O_(2) to ·OH occurs on the Pt-O-Ti interface,and the generated•OH migrates to the TiO_(2) surface to supplement the surface lattice oxygen,which sequentially oxidizes TMB to oxTMB.And the synergistic effect between Pt-O-Ti interface active sties and TiO_(2) surface active sites can significantly improve the catalytic performance.Our study provides a guide for the understanding of the intrinsic synergistic mechanism between the metal and oxide support in the metal-oxide catalysts.展开更多
LaNiO3 (LNO) thin films were prepared on Pt(111) / Ti / SiO2 / Si substrate by metal-organic decomposition (MOD) method. Pb(Zr,Ti)O3 ferroelectric thin films and their compositionally graded thin films were prepared o...LaNiO3 (LNO) thin films were prepared on Pt(111) / Ti / SiO2 / Si substrate by metal-organic decomposition (MOD) method. Pb(Zr,Ti)O3 ferroelectric thin films and their compositionally graded thin films were prepared on LNO / Pt / Ti / SiO2 /Si substrates by Sol-gel method. The composition depth profile of a typical up-graded film was determined by using a combination of Auger Electron Spectroscopy (ASE) and Ar Ion Etching. The results confirm that the processing method produces graded composition changes. XRD analysis showed that the graded thin films possessed composite structure of tetragonal and rhombohedral. The dielectric constants of Up-graded and Down-graded thin films were higher than that of each thin film unit. The dielectric constants were 277 and 269 at 10 kHz, respectively. The loss tangents were 0.019 and 0.018 at 10 kHz, respectively. The Hysteresis loops showed that the remanent polarizations of graded thin films were higher than that of each thin film unit, but the coercive fields were smaller. The remanent polarizations of Up-graded and Down-graded thin films were 30.06 and 26.96 μC·cm-2, respectively. The coercive fields were 54.14, 54.23 kV·cm-1, respectively. The pyroelectric coefficients of Up-graded and Down-graded thin films were 4.62, 2.51×10-8 C·cm-2·K-1 at room temperature, respectively. They were higher than that of each thin film unit.展开更多
基金financially supported from the National Natural Science Foundation of China(21802094,22272127,22002118,and 22172119)the National Science Fund for Distinguished Young Scholars(21825204)+1 种基金the Fundamental Research Funds for the Central Universities(D5000210666)the Natural Science Basic Research Plan in Shaanxi Province of China(2021JM-047).
文摘Identifying the active site of oxide-supported metal catalysts and revealing the intrinsic synergistic mechanism between metal and oxide support remain a large challenge.Herein,we report the identification and separation of the Pt-O-Ti interface and TiO_(2) surface in Pt-TiO_(2)-based catalysts by depositing different thickness of TiO_(2) shell with∼0.4-nm micropores onto the surface of Pt/TiO_(2) catalyst through atomic layer deposition(ALD).In the oxidation of 3,3′,5,5′-tetramethylbenzidine(TMB)by hydrogen peroxide(H_(2)O_(2))process,the TiO_(2) microporous shells can prevent the contact between TMB and embedded Pt clusters,but not delay the diffusion of H_(2)O_(2).The heterolysis of H_(2)O_(2) to ·OH occurs on the Pt-O-Ti interface,and the generated•OH migrates to the TiO_(2) surface to supplement the surface lattice oxygen,which sequentially oxidizes TMB to oxTMB.And the synergistic effect between Pt-O-Ti interface active sties and TiO_(2) surface active sites can significantly improve the catalytic performance.Our study provides a guide for the understanding of the intrinsic synergistic mechanism between the metal and oxide support in the metal-oxide catalysts.
文摘LaNiO3 (LNO) thin films were prepared on Pt(111) / Ti / SiO2 / Si substrate by metal-organic decomposition (MOD) method. Pb(Zr,Ti)O3 ferroelectric thin films and their compositionally graded thin films were prepared on LNO / Pt / Ti / SiO2 /Si substrates by Sol-gel method. The composition depth profile of a typical up-graded film was determined by using a combination of Auger Electron Spectroscopy (ASE) and Ar Ion Etching. The results confirm that the processing method produces graded composition changes. XRD analysis showed that the graded thin films possessed composite structure of tetragonal and rhombohedral. The dielectric constants of Up-graded and Down-graded thin films were higher than that of each thin film unit. The dielectric constants were 277 and 269 at 10 kHz, respectively. The loss tangents were 0.019 and 0.018 at 10 kHz, respectively. The Hysteresis loops showed that the remanent polarizations of graded thin films were higher than that of each thin film unit, but the coercive fields were smaller. The remanent polarizations of Up-graded and Down-graded thin films were 30.06 and 26.96 μC·cm-2, respectively. The coercive fields were 54.14, 54.23 kV·cm-1, respectively. The pyroelectric coefficients of Up-graded and Down-graded thin films were 4.62, 2.51×10-8 C·cm-2·K-1 at room temperature, respectively. They were higher than that of each thin film unit.
