Abstract
With the purpose of investigating the reactivity of Fe carbide as an active phase in Fischer-Tropsch catalysis, we studied the formation of a well-defined Fe carbide surface structure resulting from carbon exposure of an Fe film on Au(111). Using two different sources of carbon (C), namely atomic carbon and ethylene gas, we used synchrotron X-ray photoelectron spectroscopy (XPS) to show that a 6 ML Fe film readily converts into a well-defined and thermodynamically stable carbide phase. Scanning tunneling microscopy (STM) showed that the surface of the Fe carbide film is crystalline and is dominated by Fe(110)-like facets perturbed into a (2 × 2) periodic structure due to insertion of C in the interstitial sites. The reactivity of the carbide film toward CO, H 2 , and O 2 was furthermore probed by XPS under vacuum conditions. While the pristine Fe carbide surface was unreactive toward hydrogen gas at 500 K, we interestingly found that CO dissociation from a preadsorbed monolayer of CO takes place already at low temperature. This observation points to an intrinsic activity of the Fe carbide phase where additional carbon originating from CO can be placed in the Fe carbide surface. The catalytic significance of the model catalyst surface presented here is that it can be seen as a stable Fe carbide phase with intrinsically vacant sites for additional C insertion at elevated pressure, and we propose that such additional C may act as active species in C-C coupling reactions during FTS. The studies pave the way for a better understanding of FTS processes on Fe-based catalysts on the basis of a well-defined model surface.
| Language | English |
|---|---|
| Pages | 1264-1273 |
| Number of pages | 10 |
| Journal | ACS Catalysis |
| Volume | 9 |
| Issue number | 2 |
| DOIs | |
| State | Published - 1 Feb 2019 |
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Keywords
- carburization
- Fischer-Tropsch synthesis
- iron carbide
- model catalyst
- scanning tunneling microscopy
- X-ray photoelectron spectroscopy
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Atomically defined iron carbide surface for Fischer-Tropsch synthesis catalysis. / Li, Yijia; Li, Zheshen; Ahsen, Ali; Lammich, Lutz; Mannie, Gilbère J.A.; Niemantsverdriet, J.W.; Lauritsen, Jeppe V. (Corresponding author).
In: ACS Catalysis, Vol. 9, No. 2, 01.02.2019, p. 1264-1273.Research output: Contribution to journal › Article › Academic › peer-review
TY - JOUR
T1 - Atomically defined iron carbide surface for Fischer-Tropsch synthesis catalysis
AU - Li,Yijia
AU - Li,Zheshen
AU - Ahsen,Ali
AU - Lammich,Lutz
AU - Mannie,Gilbère J.A.
AU - Niemantsverdriet,J.W.
AU - Lauritsen,Jeppe V.
PY - 2019/2/1
Y1 - 2019/2/1
N2 - With the purpose of investigating the reactivity of Fe carbide as an active phase in Fischer-Tropsch catalysis, we studied the formation of a well-defined Fe carbide surface structure resulting from carbon exposure of an Fe film on Au(111). Using two different sources of carbon (C), namely atomic carbon and ethylene gas, we used synchrotron X-ray photoelectron spectroscopy (XPS) to show that a 6 ML Fe film readily converts into a well-defined and thermodynamically stable carbide phase. Scanning tunneling microscopy (STM) showed that the surface of the Fe carbide film is crystalline and is dominated by Fe(110)-like facets perturbed into a (2 × 2) periodic structure due to insertion of C in the interstitial sites. The reactivity of the carbide film toward CO, H 2 , and O 2 was furthermore probed by XPS under vacuum conditions. While the pristine Fe carbide surface was unreactive toward hydrogen gas at 500 K, we interestingly found that CO dissociation from a preadsorbed monolayer of CO takes place already at low temperature. This observation points to an intrinsic activity of the Fe carbide phase where additional carbon originating from CO can be placed in the Fe carbide surface. The catalytic significance of the model catalyst surface presented here is that it can be seen as a stable Fe carbide phase with intrinsically vacant sites for additional C insertion at elevated pressure, and we propose that such additional C may act as active species in C-C coupling reactions during FTS. The studies pave the way for a better understanding of FTS processes on Fe-based catalysts on the basis of a well-defined model surface.
AB - With the purpose of investigating the reactivity of Fe carbide as an active phase in Fischer-Tropsch catalysis, we studied the formation of a well-defined Fe carbide surface structure resulting from carbon exposure of an Fe film on Au(111). Using two different sources of carbon (C), namely atomic carbon and ethylene gas, we used synchrotron X-ray photoelectron spectroscopy (XPS) to show that a 6 ML Fe film readily converts into a well-defined and thermodynamically stable carbide phase. Scanning tunneling microscopy (STM) showed that the surface of the Fe carbide film is crystalline and is dominated by Fe(110)-like facets perturbed into a (2 × 2) periodic structure due to insertion of C in the interstitial sites. The reactivity of the carbide film toward CO, H 2 , and O 2 was furthermore probed by XPS under vacuum conditions. While the pristine Fe carbide surface was unreactive toward hydrogen gas at 500 K, we interestingly found that CO dissociation from a preadsorbed monolayer of CO takes place already at low temperature. This observation points to an intrinsic activity of the Fe carbide phase where additional carbon originating from CO can be placed in the Fe carbide surface. The catalytic significance of the model catalyst surface presented here is that it can be seen as a stable Fe carbide phase with intrinsically vacant sites for additional C insertion at elevated pressure, and we propose that such additional C may act as active species in C-C coupling reactions during FTS. The studies pave the way for a better understanding of FTS processes on Fe-based catalysts on the basis of a well-defined model surface.
KW - carburization
KW - Fischer-Tropsch synthesis
KW - iron carbide
KW - model catalyst
KW - scanning tunneling microscopy
KW - X-ray photoelectron spectroscopy
UR - http://www.scopus.com/inward/record.url?scp=85060236001&partnerID=8YFLogxK
U2 - 10.1021/acscatal.8b03684
DO - 10.1021/acscatal.8b03684
M3 - Article
VL - 9
SP - 1264
EP - 1273
JO - ACS Catalysis
T2 - ACS Catalysis
JF - ACS Catalysis
SN - 2155-5435
IS - 2
ER -