Technische Universitt Mnchen

First-Principles Multiscale Modelingof Catalytic Processes

Karsten Reuter

Chemistry Department and Catalysis Research CenterTechnische Universitt Mnchen

Computational screening for heterogeneous catalysis

- Mean-field microkinetic models- Assumed reaction paths- Assumed rate-determining steps- Scaling relations

J.K. Nrskov et al., Nature Chem. 1, 37 (2009)

M. Andersen, A.J. Medford, J.K. Nrskov, and K. Reuter, Angew. Chem. Int. Ed. 55, 5210 (2016)

2NO N2 + O2

Role of multiscale catalysis modeling

Descriptor ComputationalScreeningBetterCatalyst

MechanisticUnderstanding

Active sites: The effective to atomistic gap

Generic active siteindependent of operation conditionsdominant over other sites(one site model)

TMs: (111) terrace or step sites

Atomistic active site modelevery atom countsgenerally insufficient experimental characterization

Manifold of possibly active site typeson which one to focus?consider how many?

K. Reuter, C.P. Plaisance, H. Oberhofer, and M. Andersen, J. Chem. Phys. 146, 040901 (2017)

Views of heterogeneous catalysis

R. Schlgl, 20 nm Cu in10:1 H2 + O2 at 200 mbar and 523 K

K. Reuter, Cat. Lett. 146, 541 (2016)

Tolerant processes for the Energiewende

K.F. Kalz et al., Chem. Cat. Chem. 9, 17 (2017)

Multiscale catalysis modeling

Ab initio atomistic thermodynamics and statistical mechanics of surface properties and functionsK. Reuter, C. Stampfl, and M. Scheffler, in: Handbook of Materials Modeling Vol. 1,

(Ed.) S. Yip, Springer (Berlin, 2005)

Part I Insight into the active phase from in situ studiesof model catalysts

- Detailed multiscale modeling from electrons to the reactor

Part II Explicit treatment of morphological transitionsof the active surface

- Multi-lattice kinetic Monte Carlo simulations

Outline

In situ studies of model catalysts

A. Stierle and A.M. Molenbroek (Eds.), MRS Bull. 32 (2007)

P.B. Rasmussen et al., Rev. Sci. Instrum. 69, 3879 (1998)

Reactor STM

S. Yamamoto et al., J. Phys. CM 20, 184025 (2008)

in situ XPS

0.89 eV

DFT-PES for CO(cus) + O(cus)

Elementaryprocesses

Red: adsorbed O Blue: adsorbed CO

Mesoscopic statisticalinterplay

First-principles based multiscale modeling

Site

occ

upat

ion

(%)x

xx x

xx x x xxx

x

x

xxx

xx x

2po2 = 10

-10 atm

pCO (10-9 atm)

exp.

theory

0.0 1.0 2.0 3.0

Intrinsic materialfunction

Macroscopicobservable

Electronic regime: Energetics of elementary processes

COcus + Ocus CO2

- Active site model

- Level of theory

0.9 eV

M. Sabbe, M.F. Reyniers, and K. Reuter, Catal. Sci. Technol. 2, 2010 (2012)

A

B

MolecularDynamics

TS

Mesoscopic regime: Tackling rare-event time scales

kAB

kBA

kineticMonte Carlo

N

t

B

A

+=j

jijj

ijii tPktPkdt

tdP )()()(

EAB EBA

=

=

TkEZ

ZhTkk

ji

i

jiji

B

)(TSB

exp

Transition State Theory

First-principles kinetic Monte Carlo simulations for heterogeneous catalysis: Concepts, status and frontiersK. Reuter, in Modeling Heterogeneous Catalytic Reactions: From the Molecular Process to the Technical System,

(Ed.) O. Deutschmann, Wiley-VCH, Weinheim (2011)

M.J. Hoffmann, S. Matera and K. Reuter,Comp. Phys. Commun. 185, 2138 (2014)

A lattice kinetic Monte Carlo framework

Heat and mass transfer effects

T, pCO, pO2

T

pCO2

p

pO2pCO

S. Matera and K. Reuter, Catal. Lett. 133, 156 (2009)

Macroscopic regime: Accounting for the flow field

Computational Fluid Dynamicswith

chemical source termsfrom 1p-kMC

( ) 2

B

ucad

TmkpATSk

= S. Matera and K. Reuter, Phys. Rev. B 82, 085446 (2010)

Predictive surface reaction chemistry in real reactor models

S. Matera, M. Maestri, A. Cuoci, and K. Reuter,ACS Catal. 4, 4081 (2014)

together withM. Maestri and A. Cuoci

(Politecnico Milan)

Oxidation catalysis and the pressure gap: Metal, oxide, both, ?!

Nanometer and sub-nanometer thin oxide films at surfaces of late transition metals,K. Reuter, in Nanocatalysis, U. Heiz, U. Landman (Eds.), Springer, Berlin (2006).

ISBN 978-3-540-32645-8.

300K

pO (atm)2

PdO bulk

clean Pd(100)

c(22 2)R45CO/Pd(100)

O (eV)

surface oxide+ CO bridge

surface oxide+ O bridge

p CO

(at

m)

600K

surface oxide+ 2 CO bridge

C

O (e

V)

p(2x2)-O/Pd(100)

surface oxide(5 5)R27

10-15 10-10 10-5 1 105 1010

10-30 10-20 10-10 1

105

1

10-5

10-1010-30

10-20

10-10

1

0.0

-0.5

-1.0

-1.5

-2.0

-1.5 -1.0 -0.5 0.0

(1x1)CO/Pd(100)

-2.5

J. Rogal, K. Reuter, and M. Scheffler, Phys. Rev. Lett. 98, 046101 (2007); Phys. Rev. B 75, 205433 (2007)

Role of surface oxides in CO oxidation catalysis: Pd(100)

Active phases of Pd(100) in near-ambient CO oxidation catalysis:First-principles kinetic Monte Carlo models

- DFT GGA-PBE- O2 adsorption/desorption (dissociative/associative)- CO adsorption/desorption (unimolecular)- O and CO diffusion- CO + O reaction (Pd(100): LH, : LH+ER)- nearest-neighbor lateral interactions

J. Rogal, K. Reuter, and M. Scheffler, Phys. Rev. Lett. 98, 046101 (2007)J. Rogal, K. Reuter, and M. Scheffler, Phys. Rev. B 77, 155410 (2008)

M.J. Hoffmann and K. Reuter, Topics Catal. 57, 159 (2014)

In situ X-ray photoelectron spectroscopy: At the edge of the gap

together withE. Lundgren, J. Gustafson et al.

(Lund University)

1p-kMC

exp.

S. Blomberg, M.J. Hoffmann et al.,Phys. Rev. Lett. 110, 117601 (2013)

CO : O2 = 1 : 1

Laser-Induced Fluorescence (LIF)

Stimulation ofknown excitation

(here: CO2 vibration)

2D concentration profileabove catalyst

Y. Zetterberg et al., Rev. Sci. Instrum. 83, 053104 (2012)

12

6

0

y-di

rect

ion

[mm

]

400

300

200

100

0 CO

2L

IF si

gnal

[a.u

.]

-4 -2 0 2 4x-direction [mm]

E. Lundgren, J. Gustafson et al. (Lund University)

-4 -2 0 2 4x-direction [mm]

1p-kMC/CFD in action: Build-up of the boundary layer

in situ LIF measurements vs. 1p-kMC/CFD simulation ofnear-ambient CO oxidation at Pd(100)

CO : O2 = 1 : 4, ptot = 0.18 atm,T = 600 K, 72 mln/min, 50% Ar

400

300

200

100

0 CO

2L

IF si

gnal

[a.u

.]CO2

CO

Identification of the active phase through reaction product imaging

ptot = 0.18 atm72 mln/min, 50% Ar

CO : O2 = 1 : 4

Exp.

PdO(5x5)R27

Pd(100)

Functional uncertainty vs. active Pd(100) as a minority phase?!

S. Matera, S. Blomberg et al., ACS Catal. 5, 4514 (2015)

Part I Insight into the active phase from in situ studiesof model catalysts

- Detailed multiscale modeling from electrons to the reactor

Part II Explicit treatment of morphological transitionsof the active surface

- Multi-lattice kinetic Monte Carlo simulations

Outline

Lattice mapping vs. surface morphological transitions

PdO(5x5)R27Pd(100)

Different, but commensurate lattices

Multi-lattice kinetic Monte Carlo approach

Perform kMC simulations on commensurate superlatticeBlock inactive sites through occupation of null species

Toggle between phases by removal/addition of null species

M.J. Hoffmann, M. Scheffler, and K. Reuter, ACS Catal. 5, 1199 (2015)

Reduction of the Pd(100) surface oxide by CO

Reduction kinetics in pure CO environment (pCO = 5 10-11 atm)

monitored through high-resolution XPS

303 K

Strongly varying time scalesover 90K temperature range

Mean-field kinetic analysis suggestsreduction process is

phase boundary controlled

343 K

393 K

V.R. Fernandez et al., Surf. Sci. 621, 31 (2014)

Atomistic pathway for initial oxide decomposition

Divacancyformation

Oxygendiffusion

Pd(100)nucleus

Oxide reduction kinetics from first principles

343 K

Full reproduction ofexperimental trends:

- Temperature ordering- Time scales

M.J. Hoffmann, M. Scheffler, and K. Reuter, ACS Catal. 5, 1199 (2015)

Role of CO oxidation across metal/oxide boundary

Stronger CO binding at Pd(100)enhances cross-reactions at

higher temperatures

- Present set of computational tools well developed to tacklestatic catalytic problems ( computational screening)

- Addressing near-ambient in situ studies requires multiscalemodeling from electrons to the reactor

- Present microkinetic approaches fall short in scrutinizingpotentially crucial dynamicaltransformations of the activesurface. Self-fulfilling prophecy?!

Weve come a long way to reach half way

K. Reuter, Catal. Lett. 146, 541 (2016)

Technische Universitt Mnchen

www.th4.ch.tum.de

Past members:J. Rogal ( RU Bochum)M. Rieger ( BASF) M. Maestri ( U Milan)S. Matera ( FU Berlin)J. Meyer ( U Leiden)M.J. Hoffmann ( Stanford)

Collaborations:M. Scheffler (FHI Berlin)J. Gustafson, E. Lundgren (U Lund)A.J. Medford, J.K. Nrskov (Stanford)

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