TY - JOUR
T1 - How does the oxidation state of palladium surfaces affect the reactivity and selectivity of direct synthesis of hydrogen peroxide from hydrogen and oxygen gases? A density functional study
AU - Wang, Fang
AU - Xia, Chungu
AU - De Visser, Samuel
AU - Wang, Yong
N1 - Funding Information:
The authors acknowledge the financial support received from the National Natural Science Foundation of China (Project Nos. 21873052, 21173211, 21203218, and 21633013) and the open fund of the State Key Laboratory of Molecular Reaction Dynamics. The authors also gratefully acknowledge the computing resources and time made available by the Supercomputing Center of Cold and Arid Region Environment and the Engineering Research Institute of the Chinese Academy of Sciences.
Publisher Copyright:
Copyright © 2018 American Chemical Society.
PY - 2019/1/16
Y1 - 2019/1/16
N2 - Copyright © 2018 American Chemical Society. Direct synthesis of H 2 O 2 from H 2 and O 2 is an environmentally benign and atom economic process and as such is the ideal pathway in catalysis. However, currently no low-cost pathway of this kind of catalysis exists, although it would be an attractive alternative strategy to the common industrial anthraquinone method for H 2 O 2 production. Metal-based catalysts are widely employed in such a direct synthesis process but often need to be oxidized, alloyed, or supplied with additives to make them selective. To understand the metal-oxidation state in heterogeneous catalysis, we studied the selective oxidation of hydrogen by molecular oxygen on Pd(111) and PdO(101) surfaces, leading to either H 2 O 2 or H 2 O products. Our results demonstrate, for the first time, that the oxidized PdO(101) surface clearly shows better performance and selectivity, as compared to the reduced Pd(111) one. The activation barrier on the oxidized Pd surface is ca. 0.2 eV lower than the one on the reduced Pd surface. On the oxidized surface, the H 2 O 2 synthesis route is preferred, while, on the reduced surface, the H 2 O route is predominant. The decomposition of H 2 O 2 is also greatly inhibited on the oxidized surface. We analyzed the different pathways in detail through thermochemical cycles, which establishes that the oxidized surface shows weaker adsorption ability toward the reagents O 2 and H 2 , the key intermediate OOH, and also the product H 2 O 2 in comparison with the Pd(111) surface, which we believe affect the selectivity. The work presented here clearly shows that the oxidation state of metal surfaces is one of the most important factors that tunes the catalysis of a chemical reaction and can affect the selectivity and reaction patterns dramatically. ©
AB - Copyright © 2018 American Chemical Society. Direct synthesis of H 2 O 2 from H 2 and O 2 is an environmentally benign and atom economic process and as such is the ideal pathway in catalysis. However, currently no low-cost pathway of this kind of catalysis exists, although it would be an attractive alternative strategy to the common industrial anthraquinone method for H 2 O 2 production. Metal-based catalysts are widely employed in such a direct synthesis process but often need to be oxidized, alloyed, or supplied with additives to make them selective. To understand the metal-oxidation state in heterogeneous catalysis, we studied the selective oxidation of hydrogen by molecular oxygen on Pd(111) and PdO(101) surfaces, leading to either H 2 O 2 or H 2 O products. Our results demonstrate, for the first time, that the oxidized PdO(101) surface clearly shows better performance and selectivity, as compared to the reduced Pd(111) one. The activation barrier on the oxidized Pd surface is ca. 0.2 eV lower than the one on the reduced Pd surface. On the oxidized surface, the H 2 O 2 synthesis route is preferred, while, on the reduced surface, the H 2 O route is predominant. The decomposition of H 2 O 2 is also greatly inhibited on the oxidized surface. We analyzed the different pathways in detail through thermochemical cycles, which establishes that the oxidized surface shows weaker adsorption ability toward the reagents O 2 and H 2 , the key intermediate OOH, and also the product H 2 O 2 in comparison with the Pd(111) surface, which we believe affect the selectivity. The work presented here clearly shows that the oxidation state of metal surfaces is one of the most important factors that tunes the catalysis of a chemical reaction and can affect the selectivity and reaction patterns dramatically. ©
UR - http://www.scopus.com/inward/record.url?scp=85060088962&partnerID=8YFLogxK
UR - http://www.mendeley.com/research/oxidation-state-palladium-surfaces-affect-reactivity-selectivity-direct-synthesis-hydrogen-peroxide
U2 - 10.1021/jacs.8b10281
DO - 10.1021/jacs.8b10281
M3 - Article
SN - 0002-7863
VL - 141
SP - 901
EP - 910
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 2
ER -