TY - JOUR
T1 - Evolution of steady-state material properties during catalysis
T2 - Oxidative coupling of methanol over nanoporous Ag0.03Au0.97
AU - Zugic, Branko
AU - van Spronsen, Matthijs A.
AU - Heine, Christian
AU - Montemore, Matthew M.
AU - Li, Yuanyuan
AU - Zakharov, Dmitri N.
AU - Karakalos, Stavros
AU - Lechner, Barbara A.J.
AU - Crumlin, Ethan
AU - Biener, Monika M.
AU - Frenkel, Anatoly I.
AU - Biener, Juergen
AU - Stach, Eric A.
AU - Salmeron, Miquel B.
AU - Kaxiras, Efthimios
AU - Madix, Robert J.
AU - Friend, Cynthia M.
N1 - Publisher Copyright:
© 2019 Elsevier Inc.
PY - 2019/12
Y1 - 2019/12
N2 - Activating pretreatments are used to tune surface composition and structure of bimetallic-alloy catalysts. Herein, the activation-induced changes in material properties of a nanoporous Ag0.03Au0.97 alloy and their subsequent evolution under steady-state CH3OH oxidation conditions are investigated. Activation using O3 results in AgO and Au2O3, strongly enriching the near-surface region in Ag. These oxides reduce in the O2/CH3OH mixture, yielding CO2 and producing a highly Ag-enriched surface alloy. At the reaction temperature (423 K), Ag realloys gradually with Au but remains enriched (stabilized by surface O) in the top few nanometers, producing methyl formate selectively without significant deactivation. At higher temperatures, bulk diffusion induces sintering and Ag redistribution, leading to a loss of activity. These findings demonstrate that material properties determining catalytic activity are dynamic and that metastable (kinetically trapped) forms of the material may be responsible for catalysis, providing guiding principles concerning the activation of heterogeneous catalysts for selective oxidation.
AB - Activating pretreatments are used to tune surface composition and structure of bimetallic-alloy catalysts. Herein, the activation-induced changes in material properties of a nanoporous Ag0.03Au0.97 alloy and their subsequent evolution under steady-state CH3OH oxidation conditions are investigated. Activation using O3 results in AgO and Au2O3, strongly enriching the near-surface region in Ag. These oxides reduce in the O2/CH3OH mixture, yielding CO2 and producing a highly Ag-enriched surface alloy. At the reaction temperature (423 K), Ag realloys gradually with Au but remains enriched (stabilized by surface O) in the top few nanometers, producing methyl formate selectively without significant deactivation. At higher temperatures, bulk diffusion induces sintering and Ag redistribution, leading to a loss of activity. These findings demonstrate that material properties determining catalytic activity are dynamic and that metastable (kinetically trapped) forms of the material may be responsible for catalysis, providing guiding principles concerning the activation of heterogeneous catalysts for selective oxidation.
KW - Diluted alloys
KW - In situ/operando multimodal approach
KW - Metastability
KW - Nanoporous Au
KW - Selective oxidation of CHOH
UR - http://www.scopus.com/inward/record.url?scp=85073990901&partnerID=8YFLogxK
U2 - 10.1016/j.jcat.2019.08.041
DO - 10.1016/j.jcat.2019.08.041
M3 - Article
AN - SCOPUS:85073990901
SN - 0021-9517
VL - 380
SP - 366
EP - 374
JO - Journal of Catalysis
JF - Journal of Catalysis
ER -