TY - JOUR
T1 - Strong electrostatic adsorption of Pt onto SiO2 partially overcoated Al2O3 - Towards single atom catalysts
AU - Bo, Zhenyu
AU - McCullough, Lauren R.
AU - Dull, Samuel
AU - Ardagh, M. Alexander
AU - Wang, Jie
AU - Notestein, Justin
N1 - Funding Information:
This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Science, under Award No. DOE DE-FG02-03ER15457 to the Institute for Catalysis for Energy Processes (ICEP) at Northwestern University. DRIFTS, chemisorption, and reaction studies were carried out at the REACT facility at Northwestern University. Metal analysis was carried out in the Northwestern University Quantitative Bio-element Imaging Center. STEM and TEM were carried out at the Center for Nanomaterials at Argonne National Laboratory. Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Publisher Copyright:
© 2019 Author(s).
PY - 2019/12/7
Y1 - 2019/12/7
N2 - It is frequently desired to synthesize supported metal catalysts that consist of very small clusters or single atoms. In this work, we combine strong electrostatic adsorption (SEA) of H2PtCl6 and engineered oxide supports to ultimately produce very small Pt clusters, including a large fraction of single Pt atoms. The supports are synthesized by depositing controlled amounts of SiO2 onto Al2O3 (SiO2@Al2O3) that has been previously grafted with bulky organic templates. After the templates are removed, the oxide supports are largely negatively charged, like SiO2, but have small patches of positively charged Al2O3, derived from the regions previously covered by the template. The overall point of zero charge of these materials decreases from pH 6.4 for 1 cycle of SiO2 deposition to a SiO2-like <2 for materials with more than 5 cycles of SiO2 deposition. SEA at pH 4 on templated SiO2@Al2O3 deposits from 1 wt. % to 0.05 wt. % Pt as the amount of SiO2 increases. Pt loadings drop to near zero in the absence of a template. The resulting Pt nanoparticles are generally <1 nm and have dispersion near 100% by CO chemisorption. Finally, CO DRIFTS shows that the CO nanoparticles become increasingly well defined and have a higher percentage of Pt single atoms as the amount of SiO2 increases on the SiO2@Al2O3 particles. Overall, this method of synthesizing patches of charge on a carrier particle appears to be a viable route to creating extremely highly dispersed supported metal catalysts.
AB - It is frequently desired to synthesize supported metal catalysts that consist of very small clusters or single atoms. In this work, we combine strong electrostatic adsorption (SEA) of H2PtCl6 and engineered oxide supports to ultimately produce very small Pt clusters, including a large fraction of single Pt atoms. The supports are synthesized by depositing controlled amounts of SiO2 onto Al2O3 (SiO2@Al2O3) that has been previously grafted with bulky organic templates. After the templates are removed, the oxide supports are largely negatively charged, like SiO2, but have small patches of positively charged Al2O3, derived from the regions previously covered by the template. The overall point of zero charge of these materials decreases from pH 6.4 for 1 cycle of SiO2 deposition to a SiO2-like <2 for materials with more than 5 cycles of SiO2 deposition. SEA at pH 4 on templated SiO2@Al2O3 deposits from 1 wt. % to 0.05 wt. % Pt as the amount of SiO2 increases. Pt loadings drop to near zero in the absence of a template. The resulting Pt nanoparticles are generally <1 nm and have dispersion near 100% by CO chemisorption. Finally, CO DRIFTS shows that the CO nanoparticles become increasingly well defined and have a higher percentage of Pt single atoms as the amount of SiO2 increases on the SiO2@Al2O3 particles. Overall, this method of synthesizing patches of charge on a carrier particle appears to be a viable route to creating extremely highly dispersed supported metal catalysts.
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U2 - 10.1063/1.5128934
DO - 10.1063/1.5128934
M3 - Article
C2 - 31822069
AN - SCOPUS:85076337403
VL - 151
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
SN - 0021-9606
IS - 21
M1 - 214703
ER -