Using the in-situ liquid cell transmission electron microscopy, the three-stage growth of Pt3Ni-Ni(OH)2 core-shell structures at the gas-liquid interfaces was clearly observed, which consists of(1) a thermodynamically...Using the in-situ liquid cell transmission electron microscopy, the three-stage growth of Pt3Ni-Ni(OH)2 core-shell structures at the gas-liquid interfaces was clearly observed, which consists of(1) a thermodynamically driven Pt3Ni alloy core by the monomer attachment,(2) a nickel(Ni) shell formation due to the depletion of the Pt salt precursor, and(3) the oxidation and of the Ni shell into Ni(OH)2 flakes. We also further observed the nucleation and growth of the Ni(OH)2 flakes on an existing layer either at the middle part or at the step edge. More interestingly, the dynamic transformation among a Pt3Ni alloy, Ni clusters and Ni(OH)2 flakes was also imaged even at a high electron dose rate.展开更多
The preparation of highly active supported noble metal catalysts with a low noble metal loading has always been the ultimate goal of researchers working on catalysis.Hydrothermally treated Pt/Al_(2)O_(3)(Pt/Al_(2)O_(3...The preparation of highly active supported noble metal catalysts with a low noble metal loading has always been the ultimate goal of researchers working on catalysis.Hydrothermally treated Pt/Al_(2)O_(3)(Pt/Al_(2)O_(3)-H)exhibits better catalytic activity than that(Pt/Al_(2)O_(3)-C)treated via the conventional calcination approach.At the high space velocity of100,000 m L/(g·hr),the temperature that correspond to 50%toluene conversion(T50)of Pt/Al_(2)O_(3)-H is 115℃ lower than that of Pt/Al_(2)O_(3)-C,and the turnover frequency(TOF)value can reach 0.0756 sec-1.The mechanism by which the hydrothermal approach enhances Pt/Al_(2)O_(3) activity has been investigated.The structure associated with the high catalytic activity of Pt nanoparticles(NPs)can be retained via hydrothermal treatment.Furthermore,the support is transformed to AlO(OH)with numerous surface hydroxyl groups,which in turn can facilitate the adsorption of toluene.And the synergistic effects of Pt NPs and AlO(OH)increases the contents of Pt in oxidation state and active oxygen,which are beneficial for toluene oxidation.展开更多
基金the National Key Research and Development Program of China(2017YFA0206500)the National Natural Science Foundation of China(21673198,21373008,21621091)。
文摘Using the in-situ liquid cell transmission electron microscopy, the three-stage growth of Pt3Ni-Ni(OH)2 core-shell structures at the gas-liquid interfaces was clearly observed, which consists of(1) a thermodynamically driven Pt3Ni alloy core by the monomer attachment,(2) a nickel(Ni) shell formation due to the depletion of the Pt salt precursor, and(3) the oxidation and of the Ni shell into Ni(OH)2 flakes. We also further observed the nucleation and growth of the Ni(OH)2 flakes on an existing layer either at the middle part or at the step edge. More interestingly, the dynamic transformation among a Pt3Ni alloy, Ni clusters and Ni(OH)2 flakes was also imaged even at a high electron dose rate.
基金supported by the National Natural Science Foundation of China(Nos.21506194,21676255)the Zhejiang Provincial Natural Science Foundation of China(Nos.LZ21E080001,2017C03007,2017C33106)。
文摘The preparation of highly active supported noble metal catalysts with a low noble metal loading has always been the ultimate goal of researchers working on catalysis.Hydrothermally treated Pt/Al_(2)O_(3)(Pt/Al_(2)O_(3)-H)exhibits better catalytic activity than that(Pt/Al_(2)O_(3)-C)treated via the conventional calcination approach.At the high space velocity of100,000 m L/(g·hr),the temperature that correspond to 50%toluene conversion(T50)of Pt/Al_(2)O_(3)-H is 115℃ lower than that of Pt/Al_(2)O_(3)-C,and the turnover frequency(TOF)value can reach 0.0756 sec-1.The mechanism by which the hydrothermal approach enhances Pt/Al_(2)O_(3) activity has been investigated.The structure associated with the high catalytic activity of Pt nanoparticles(NPs)can be retained via hydrothermal treatment.Furthermore,the support is transformed to AlO(OH)with numerous surface hydroxyl groups,which in turn can facilitate the adsorption of toluene.And the synergistic effects of Pt NPs and AlO(OH)increases the contents of Pt in oxidation state and active oxygen,which are beneficial for toluene oxidation.
