First-Principles Simulation and Model-Driven Isotopic Labeling Experiments
Reveal Biomass Decomposition Pathways1
Theory driven experimental confirmation
Potential decomposition pathways of C2H6O2 on Pt(111)
C2 H6O2 (g)
-1
HOCH2 CHOH*
HOCHCH2O*
TS3c
HOCHCHO*
TS3a
TS4a
HOCH2CHO
TS3b
HOCH2COH*
TS4b
TS2b
C2 H6O 2 *
OCCH 2O*
TS5b
TS6d
TS5a
TS6b
DOCH2CH2OD
322K
432K
HOCD2CD2OH
346K
HOCH2 CO*
OCCHO* TS6a
HOCHCO*
-2
(B)
H2(2amu)
HD(3amu)
398K
398K
Intensity (arb. units)
0
(A)
HOCH2CH2 O*
TS2a
TS1b
TS2c
TS1a
Intensity (arb. units)
300K
DOCH2CH2OD
444K
HOCD2CD2OH
background
OCCO*
250
HOCCO*
300
350
400
450
500
550
600
250
300
350
400
450
500
550
600
Temperature (K)
Temperature (K)
HCO*+CO*
2CO*
-4
Initial O-H bond cleavage is favored energetically over initial
C-H bond cleavage. Further, downstream C-C bond cleaving
barriers are lower than initial dehydrogenation barriers
Key Findings:
• Density functional theory (DFT) calculations of ethylene glycol
decomposition on Pt(111) and Ni/Pt(111) reveal key differences
between decomposition of highly functionalized oxygenates compared
to mono-alcohols and hydrocarbons
• Very low C-C scission barriers exist for highly dehydrogenated
C2HXO2 surface intermediates
• Highest barriers correspond to early O-H and C-H reactions
• Reaction pathway changes between Pt and more active Ni/Pt
• Decomposition on Pt proceeds through initial O-H bond cleavage
followed by scission of C-H and O-H bonds
• Ethylene glycol decomposition on Ni-Pt-Pt shows formation of the
1,2-dioxyethylene (both O-H bonds break initially) (right)
1
Temperature programmed
desorption (TPD) of
deuterated ethylene glycols
confirms that reaction
occurs through initial O-H
bond cleavage, followed
by C-H and O-H bond
cleavage on Pt(111).
(C)
D2(4amu)
300K
402K
Intensity (arb. units)
-3
DOCH2CH2OD
457K
HOCD2CD2OH
250
300
350
400
450
500
550
600
Temperature (K)
DFT comparison of pathways over Pt and Ni/Pt
1
Electronic Energy [eV]
Electronic energy [eV]
1
0
Pt(111)
Ni/Pt(111)
C2H6O2(g)
C2H6O2*
TS2a
TS2b
TS1a
HOCH2CH2O* TS2d
TS1d
-1
OCH2CH2O*
TS2c
TS2e
TS2f
C2H6O2*
HOCH2CH2O*
HOCHCH2O*
HOCH2CHO*
HOCHCH2O*
OCH2CH2O*
HOCH2CHO*
-2
M. Salciccioli, W. Yu, M.A. Barteau, J.G. Chen, D.G. Vlachos, J. Am. Chem. Soc. In Press