TY - JOUR
T1 - Acetylene Reactivity on Pd-Cu Nanoparticles Supported on Thin Silica Films
T2 - The Role of the Underlying Substrate
AU - Sorek, E.
AU - Ankri, J.
AU - Arbiv, G.
AU - Mol, R.
AU - Popov, I.
AU - Freund, H. J.
AU - Shaikhutdinov, S.
AU - Asscher, M.
N1 - Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/6/25
Y1 - 2019/6/25
N2 - Heterogeneous chemistry that develops on ultrathin films such as bilayer SiO2/Ru(0001) is interesting as a model catalysis system. We have studied the partial decomposition and hydrogenation of acetylene to ethylene and its trimerization to benzene on Pd-Cu bimetallic alloy nanoparticles (NPs) supported on those thin silica films. In comparing the bilayer SiO2/Ru(0001) to thicker silica layers without a metallic substrate, for example, the native SiO2/Si(100), the size distribution of the clusters is narrower on the bilayer SiO2/Ru(0001) substrate, demonstrating the effect of the underlying metal in preventing cluster diffusion during their growth. In addition, the effect of medium pressure on the NP shape has been investigated via transmission electron microscopy imaging of the NPs on relatively thick SiO2. The NPs become elongated when exposed to 0.2 mbar acetylene inside a moderate-pressure cell embedded within an ultrahigh vacuum (UHV) chamber. By changing the elemental composition of the NPs on both substrates, the important effect of the suboxide material on catalyst reaction selectivity has been demonstrated. However, the effect of the composition of the bare NPs is not enough to actually define the long-term activity of a catalyst. In order to address more realistic conditions, we performed consecutive reactivity cycles by adsorbing acetylene at 110 K with subsequent annealing up to 400 K in UHV on the same 1Pd:1Cu NPs/bilayer SiO2/Ru(0001) catalyst. This revealed a strong decrease in the selectivity toward ethylene, from an ethylene/benzene product yield ratio of 370 ± 150 in the first cycle down to 50 ± 15 during the third to fifth cycles. Carbon atom accumulation on the metallic particles in the first and subsequent runs is the main reason for this modification in selectivity. A consecutive reactivity study uniquely demonstrates how rapidly and significantly the catalyst's performance is modified during the initial stages of its heterogeneous catalytic reactivity.
AB - Heterogeneous chemistry that develops on ultrathin films such as bilayer SiO2/Ru(0001) is interesting as a model catalysis system. We have studied the partial decomposition and hydrogenation of acetylene to ethylene and its trimerization to benzene on Pd-Cu bimetallic alloy nanoparticles (NPs) supported on those thin silica films. In comparing the bilayer SiO2/Ru(0001) to thicker silica layers without a metallic substrate, for example, the native SiO2/Si(100), the size distribution of the clusters is narrower on the bilayer SiO2/Ru(0001) substrate, demonstrating the effect of the underlying metal in preventing cluster diffusion during their growth. In addition, the effect of medium pressure on the NP shape has been investigated via transmission electron microscopy imaging of the NPs on relatively thick SiO2. The NPs become elongated when exposed to 0.2 mbar acetylene inside a moderate-pressure cell embedded within an ultrahigh vacuum (UHV) chamber. By changing the elemental composition of the NPs on both substrates, the important effect of the suboxide material on catalyst reaction selectivity has been demonstrated. However, the effect of the composition of the bare NPs is not enough to actually define the long-term activity of a catalyst. In order to address more realistic conditions, we performed consecutive reactivity cycles by adsorbing acetylene at 110 K with subsequent annealing up to 400 K in UHV on the same 1Pd:1Cu NPs/bilayer SiO2/Ru(0001) catalyst. This revealed a strong decrease in the selectivity toward ethylene, from an ethylene/benzene product yield ratio of 370 ± 150 in the first cycle down to 50 ± 15 during the third to fifth cycles. Carbon atom accumulation on the metallic particles in the first and subsequent runs is the main reason for this modification in selectivity. A consecutive reactivity study uniquely demonstrates how rapidly and significantly the catalyst's performance is modified during the initial stages of its heterogeneous catalytic reactivity.
UR - http://www.scopus.com/inward/record.url?scp=85070277292&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcc.9b04722
DO - 10.1021/acs.jpcc.9b04722
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AN - SCOPUS:85070277292
SN - 1932-7447
VL - 123
SP - 17425
EP - 17431
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 28
ER -