Mixed metal oxides of earth-abundant 3d transition metals are an interesting class of materials that show interesting magnetic properties and a significant synergistic effect as catalysts for electrochemical oxygen evolution compared to simple unary oxides. However, the exact atomic-scale nature of such mixed oxide phases and the link to their interesting physico-chemical properties are poorly understood. Here, a combination of scanning tunneling microscopy and x-ray photoemission spectroscopy reveals that Fe species embed in a facile way into CoO bilayers on Au(111) resulting in an Fe doped oxide. Density functional theory and the spectroscopic fingerprint from x-ray photoemission spectroscopy reveal that the Fe dopants in the cobalt oxide matrix assume a higher oxidation state than in the structurally corresponding unary bilayer oxide. Furthermore, the substituted Fe is structurally displaced further away from the Au than the metal in either of the corresponding pure unary oxides. Both O and to a smaller extent Co in the nearest coordination shell are also structurally and electronically perturbed. The interesting effects observed in the bilayer binary oxides may enable a better fundamental understanding of the nature of doping of metal oxides, in general, and promotion effects in catalytic applications.

1.
R.
Subbaraman
,
D.
Tripkovic
,
K. C.
Chang
,
D.
Strmcnik
,
A. P.
Paulikas
,
P.
Hirunsit
,
M.
Chan
,
J.
Greeley
,
V.
Stamenkovic
, and
N. M.
Markovic
,
Nat. Mater.
11
(
6
),
550
557
(
2012
).
2.
I. C.
Man
,
H.-Y.
Su
,
F.
Calle-Vallejo
,
H. A.
Hansen
,
J. I.
Martínez
,
N. G.
Inoglu
,
J.
Kitchin
,
T. F.
Jaramillo
,
J. K.
Nørskov
, and
J.
Rossmeisl
,
ChemCatChem
3
(
7
),
1159
1165
(
2011
).
3.
Y.
Ren
,
Z.
Ma
,
L.
Qian
,
S.
Dai
,
H.
He
, and
P. G.
Bruce
,
Catal. Lett.
131
(
1
),
146
154
(
2009
).
4.
L.
Trotochaud
,
J. K.
Ranney
,
K. N.
Williams
, and
S. W.
Boettcher
,
J. Am. Chem. Soc.
134
(
41
),
17253
17261
(
2012
).
5.
J.
Rosen
,
G. S.
Hutchings
, and
F.
Jiao
,
J. Am. Chem. Soc.
135
(
11
),
4516
4521
(
2013
).
6.
W.
Chen
,
Y.
Liu
,
Y.
Li
,
J.
Sun
,
Y.
Qiu
,
C.
Liu
,
G.
Zhou
, and
Y.
Cui
,
Nano Lett.
16
(
12
),
7588
7596
(
2016
).
7.
G.
Wang
,
Y.
Ling
,
D. A.
Wheeler
,
K. E.
George
,
K.
Horsley
,
C.
Heske
,
J. Z.
Zhang
, and
Y.
Li
,
Nano Lett.
11
(
8
),
3503
3509
(
2011
).
8.
G.
Wu
,
N.
Li
,
D.-R.
Zhou
,
K.
Mitsuo
, and
B.-Q.
Xu
,
J. Solid State Chem.
177
(
10
),
3682
3692
(
2004
).
9.
M. S.
Burke
,
L. J.
Enman
,
A. S.
Batchellor
,
S.
Zou
, and
S. W.
Boettcher
,
Chem. Mater.
27
(
22
),
7549
7558
(
2015
).
10.
L.
Trotochaud
,
S. L.
Young
,
J. K.
Ranney
, and
S. W.
Boettcher
,
J. Am. Chem. Soc.
136
(
18
),
6744
6753
(
2014
).
11.
S.
Klaus
,
M. W.
Louie
,
L.
Trotochaud
, and
A. T.
Bell
,
J. Phys. Chem. C
119
(
32
),
18303
18316
(
2015
).
12.
A. L.
Strickler
,
M. A.
Escudero-Escribano
, and
T. F.
Jaramillo
,
Nano Lett.
17
(
10
),
6040
6046
(
2017
).
13.
J. T.
Ren
,
G. G.
Yuan
,
C. C.
Weng
,
L.
Chen
, and
Z. Y.
Yuan
,
Nanoscale
10
(
22
),
10620
10628
(
2018
).
14.
A. C.
Pebley
,
E.
Decolvenaere
,
T. M.
Pollock
, and
M. J.
Gordon
,
Nanoscale
9
(
39
),
15070
15082
(
2017
).
15.
S.
Klaus
,
Y.
Cai
,
M. W.
Louie
,
L.
Trotochaud
, and
A. T.
Bell
,
J. Phys. Chem. C
119
(
13
),
7243
7254
(
2015
).
16.
J.
Fester
,
A.
Makoveev
,
D.
Grumelli
,
R.
Gutzler
,
Z.
Sun
,
J.
Rodriguez-Fernandez
,
K.
Kern
, and
J. V.
Lauritsen
,
Angew. Chem., Int. Ed.
57
(
37
),
11893
11897
(
2018
).
17.
D.
Friebel
,
M. W.
Louie
,
M.
Bajdich
,
K. E.
Sanwald
,
Y.
Cai
,
A. M.
Wise
,
M. J.
Cheng
,
D.
Sokaras
,
T. C.
Weng
,
R.
Alonso-Mori
,
R. C.
Davis
,
J. R.
Bargar
,
J. K.
Norskov
,
A.
Nilsson
, and
A. T.
Bell
,
J. Am. Chem. Soc.
137
(
3
),
1305
1313
(
2015
).
18.
B. J.
Trzesniewski
,
O.
Diaz-Morales
,
D. A.
Vermaas
,
A.
Longo
,
W.
Bras
,
M. T.
Koper
, and
W. A.
Smith
,
J. Am. Chem. Soc.
137
(
48
),
15112
15121
(
2015
).
19.
F.
Song
and
X.
Hu
,
Nat. Commun.
5
,
4477
(
2014
).
20.
M. S.
Burke
,
M. G.
Kast
,
L.
Trotochaud
,
A. M.
Smith
, and
S. W.
Boettcher
,
J. Am. Chem. Soc.
137
(
10
),
3638
3648
(
2015
).
21.
J. G.
Kim
,
Y.
Noh
,
Y.
Kim
,
S.
Lee
, and
W. B.
Kim
,
Nanoscale
9
(
16
),
5119
5128
(
2017
).
22.
Z.
Zhou
,
Y.
Zhang
,
Z.
Wang
,
W.
Wei
,
W.
Tang
,
J.
Shi
, and
R.
Xiong
,
Appl. Surf. Sci.
254
(
21
),
6972
6975
(
2008
).
23.
Y. H.
Hou
,
Y. J.
Zhao
,
Z. W.
Liu
,
H. Y.
Yu
,
X. C.
Zhong
,
W. Q.
Qiu
,
D. C.
Zeng
, and
L. S.
Wen
,
J. Phys. D: Appl. Phys.
43
(
44
),
445003
(
2010
).
24.
M.
Haneda
,
Y.
Kawaguchi
, and
A.
Towata
,
J. Ceram. Soc. Jpn.
125
(
3
),
135
140
(
2017
).
25.
P.
Mountapmbeme Kouotou
,
H.
Vieker
,
Z. Y.
Tian
,
P. H.
Tchoua Ngamou
,
A.
El Kasmi
,
A.
Beyer
,
A.
Gölzhäuser
, and
K.
Kohse-Höinghaus
,
Catal. Sci. Technol.
4
(
9
),
3359
(
2014
).
26.
V.
Tripkovic
,
H. A.
Hansen
, and
T.
Vegge
,
ACS Catal.
7
(
12
),
8558
8571
(
2017
).
27.
F.
Song
and
X.
Hu
,
J. Am. Chem. Soc.
136
(
47
),
16481
16484
(
2014
).
28.
F.
Cheng
,
J.
Shen
,
B.
Peng
,
Y.
Pan
,
Z.
Tao
, and
J.
Chen
,
Nat. Chem.
3
(
1
),
79
84
(
2011
).
29.
J.
Fester
,
A.
Walton
,
Z.
Li
, and
J. V.
Lauritsen
,
Phys. Chem. Chem. Phys.
19
(
3
),
2425
2433
(
2017
).
30.
J.
Fester
,
M.
Garcia-Melchor
,
A. S.
Walton
,
M.
Bajdich
,
Z.
Li
,
L.
Lammich
,
A.
Vojvodic
, and
J. V.
Lauritsen
,
Nat. Commun.
8
,
14169
(
2017
).
31.
J.
Fester
,
M.
Bajdich
,
A. S.
Walton
,
Z.
Sun
,
P. N.
Plessow
,
A.
Vojvodic
, and
J. V.
Lauritsen
,
Top. Catal.
60
(
6-7
),
503
512
(
2016
).
32.
W.
Kudernatsch
,
G.
Peng
,
H.
Zeuthen
,
Y.
Bai
,
L. R.
Merte
,
L.
Lammich
,
F.
Besenbacher
,
M.
Mavrikakis
, and
S.
Wendt
,
ACS Nano
9
(
8
),
7804
7814
(
2015
).
33.
L.
Gragnaniello
,
S.
Agnoli
,
G.
Parteder
,
A.
Barolo
,
F.
Bondino
,
F.
Allegretti
,
S.
Surnev
,
G.
Granozzi
, and
F. P.
Netzer
,
Surf. Sci.
604
(
21-22
),
2002
2011
(
2010
).
34.
D.
Kuhness
,
S.
Pomp
,
V.
Mankad
,
G.
Barcaro
,
L.
Sementa
,
A.
Fortunelli
,
F. P.
Netzer
, and
S.
Surnev
,
Surf. Sci.
645
,
13
22
(
2016
).
35.
L.
Giordano
,
G.
Pacchioni
,
J.
Goniakowski
,
N.
Nilius
,
E. D. L.
Rienks
, and
H.-J.
Freund
,
Phys. Rev. B
76
(
7
),
075416
(
2007
).
36.
L. R.
Merte
,
M.
Shipilin
,
S.
Ataran
,
S.
Blomberg
,
C.
Zhang
,
A.
Mikkelsen
,
J.
Gustafson
, and
E.
Lundgren
,
J. Phys. Chem. C
119
(
5
),
2572
2582
(
2015
).
37.
Q.
Fu
,
W.-X.
Li
,
Y.
Yao
,
H.
Liu
,
H.-Y.
Su
,
D.
Ma
,
X.-K.
Gu
,
L.
Chen
,
Z.
Wang
,
H.
Zhang
,
B.
Wang
, and
X.
Bao
,
Science
328
(
5982
),
1141
(
2010
).
38.
G.
Zhao
,
F.
Yang
,
Z.
Chen
,
Q.
Liu
,
Y.
Ji
,
Y.
Zhang
,
Z.
Niu
,
J.
Mao
,
X.
Bao
,
P.
Hu
, and
Y.
Li
,
Nat. Commun.
8
,
14039
(
2017
).
39.
L. C.
Seitz
,
T. J.
Hersbach
,
D.
Nordlund
, and
T. F.
Jaramillo
,
J. Phys. Chem. Lett.
6
(
20
),
4178
4183
(
2015
).
40.
B. S.
Yeo
and
A. T.
Bell
,
J. Am. Chem. Soc.
133
(
14
),
5587
5593
(
2011
).
41.
R.
Frydendal
,
L. C.
Seitz
,
D.
Sokaras
,
T. C.
Weng
,
D.
Nordlund
,
I.
Chorkendorff
,
I. E. L.
Stephens
, and
T. F.
Jaramillo
,
Electrochim. Acta
230
,
22
28
(
2017
).
42.
R.
Frydendal
,
M.
Busch
,
N. B.
Halck
,
E. A.
Paoli
,
P.
Krtil
,
I.
Chorkendorff
, and
J.
Rossmeisl
,
ChemCatChem
7
(
1
),
149
154
(
2015
).
43.
S. L.
Dudarev
,
G. A.
Botton
,
S. Y.
Savrasov
,
C. J.
Humphreys
, and
A. P.
Sutton
,
Phys. Rev. B
57
(
3
),
1505
1509
(
1998
).
44.
G.
Kresse
and
J.
Furthmüller
,
Comput. Mater. Sci.
6
(
1
),
15
50
(
1996
).
45.
G.
Kresse
and
J.
Hafner
,
Phys. Rev. B
47
(
1
),
558
561
(
1993
).
46.
A. S.
Walton
,
J.
Fester
,
M.
Bajdich
,
M. A.
Arman
,
J.
Osiecki
,
J.
Knudsen
,
A.
Vojvodic
, and
J. V.
Lauritsen
,
ACS Nano
9
(
3
),
2445
2453
(
2015
).
47.
G.
Kresse
and
D.
Joubert
,
Phys. Rev. B
59
(
3
),
1758
1775
(
1999
).
48.
J. P.
Perdew
,
K.
Burke
, and
M.
Ernzerhof
,
Phys. Rev. Lett.
77
(
18
),
3865
3868
(
1996
).
49.
J.
Fester
,
Z.
Sun
,
J.
Rodriguez-Fernandez
,
A.
Walton
, and
J. V.
Lauritsen
,
J. Phys. Chem. B
122
,
561
(
2018
).
50.
N. A.
Khan
and
C.
Matranga
,
Surf. Sci.
602
(
4
),
932
942
(
2008
).
51.
T.
Yamashita
and
P.
Hayes
,
Appl. Surf. Sci.
254
(
8
),
2441
2449
(
2008
).
52.
T.
Fujii
,
F. M. F.
de Groot
,
G. A.
Sawatzky
,
F. C.
Voogt
,
T.
Hibma
, and
K.
Okada
,
Phys. Rev. B
59
(
4
),
3195
3202
(
1999
).
53.
P. C. J.
Graat
and
M. A. J.
Somers
,
Appl. Surf. Sci.
100-101
(
Suppl. C
),
36
40
(
1996
).
54.
X.
Deng
and
C.
Matranga
,
J. Phys. Chem. C
113
(
25
),
11104
11109
(
2009
).
55.
R.
Bliem
,
J.
Pavelec
,
O.
Gamba
,
E.
McDermott
,
Z.
Wang
,
S.
Gerhold
,
M.
Wagner
,
J.
Osiecki
,
K.
Schulte
,
M.
Schmid
,
P.
Blaha
,
U.
Diebold
, and
G. S.
Parkinson
,
Phys. Rev. B
92
(
7
),
075440
(
2015
).
56.
M. W.
Chase
and
S. National Institute of and Technology
,
NIST-JANAF Thermochemical Tables
(
American Chemical Society, American Institute of Physics for the National Institute of Standards and Technology
,
Washington, D.C., Woodbury, N.Y.
,
1998
).
57.
L. R.
Merte
,
L. C.
Grabow
,
G.
Peng
,
J.
Knudsen
,
H.
Zeuthen
,
W.
Kudernatsch
,
S.
Porsgaard
,
E.
Lægsgaard
,
M.
Mavrikakis
, and
F.
Besenbacher
,
J. Phys. Chem. C
115
(
5
),
2089
2099
(
2011
).
58.
H.
Mönig
,
M.
Todorović
,
M. Z.
Baykara
,
T. C.
Schwendemann
,
L.
Rodrigo
,
E. I.
Altman
,
R.
Pérez
, and
U. D.
Schwarz
,
ACS Nano
7
(
11
),
10233
10244
(
2013
).

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