TY - JOUR
T1 - Ultrasmall gold nanoparticles confined in zeolite Y
T2 - Preparation and activity in CO oxidation
AU - Chen, Yi Hsiu
AU - Mou, Chung Yuan
AU - Wan, Ben Zu
N1 - Funding Information:
Financial support from Ministry of Science and Technology of Taiwan and the advices from Professor Soofin Cheng and Mr. Guan-Yu Tung are appreciated. The authors thank Wen-Feng Chang for ICP-MS measurements, Hsiu-Wei Cheng, Jui-Ting Chen and Chien-Cheng Chen for technical supports of XPS, Yi-Jen Yu for HRTEM and Jeng-Lung Chen for XAS.
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2017
Y1 - 2017
N2 - In this study, proton-type zeolites Y (HY) with Al/Si ratio of 0.36 were used as a support for deposition of HAuCl4 (in pH 6 solution) to prepare Au/Y catalysts for CO oxidation at 25 °C. The low isoelectric point of HY (∼pH = 2) made this support inappropriate for loading negatively charged gold complexes, and caused the generation of large gold particles with low catalytic activity. We found that through a Na+ pretreatment of HY to form H(Na)Y, the surface charge can be reversed to positive, thus favoring the deposition. The resulting Au/H(Na)Y, without any high temperature treatment, gave excellent activity in CO oxidation comparable to Au/TiO2. The CO oxidation rate of 0.21 mol CO/mol Au∙s remained stable at 25 °C. HRTEM images of the catalyst show highly dispersed gold nanoparticles ∼1 nm confined in the nanocage of H(Na)Y. XPS spectra show high proportion of Au(III) associated with Au-O. The weak Au-O in Au/H(Na)Y is found responsible for the easy reduction in TPR. For comparison, the other alternative procedures of gold deposition were also tried to reverse the surface charge of HY by decreasing the pH of solution. However, high contents of residual Cl in the nano-gold catalyst lead to almost no activity in CO oxidation.
AB - In this study, proton-type zeolites Y (HY) with Al/Si ratio of 0.36 were used as a support for deposition of HAuCl4 (in pH 6 solution) to prepare Au/Y catalysts for CO oxidation at 25 °C. The low isoelectric point of HY (∼pH = 2) made this support inappropriate for loading negatively charged gold complexes, and caused the generation of large gold particles with low catalytic activity. We found that through a Na+ pretreatment of HY to form H(Na)Y, the surface charge can be reversed to positive, thus favoring the deposition. The resulting Au/H(Na)Y, without any high temperature treatment, gave excellent activity in CO oxidation comparable to Au/TiO2. The CO oxidation rate of 0.21 mol CO/mol Au∙s remained stable at 25 °C. HRTEM images of the catalyst show highly dispersed gold nanoparticles ∼1 nm confined in the nanocage of H(Na)Y. XPS spectra show high proportion of Au(III) associated with Au-O. The weak Au-O in Au/H(Na)Y is found responsible for the easy reduction in TPR. For comparison, the other alternative procedures of gold deposition were also tried to reverse the surface charge of HY by decreasing the pH of solution. However, high contents of residual Cl in the nano-gold catalyst lead to almost no activity in CO oxidation.
KW - CO oxidation
KW - Gold catalyst
KW - Proton-type zeolite Y (HY)
KW - Surface charge
KW - Surface modification
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U2 - 10.1016/j.apcatb.2017.06.083
DO - 10.1016/j.apcatb.2017.06.083
M3 - Article
AN - SCOPUS:85021969772
SN - 0926-3373
VL - 218
SP - 506
EP - 514
JO - Applied Catalysis B: Environmental
JF - Applied Catalysis B: Environmental
ER -