TY - JOUR

T1 - Interplay between CO Disproportionation and Oxidation

T2 - On the Origin of the CO Reaction Onset on Atomic Layer Deposition-Grown Pt/ZrO2 Model Catalysts

AU - Pramhaas, Verena

AU - Roiaz, Matteo

AU - Bosio, Noemi

AU - Corva, Manuel

AU - Rameshan, Christoph

AU - Vesselli, Erik

AU - Grönbeck, Henrik

AU - Rupprechter, Günther

N1 - Publisher Copyright: © 2020 American Chemical Society.

PY - 2021/1/1

Y1 - 2021/1/1

N2 - Pt/ZrO2 model catalysts were prepared by atomic layer deposition (ALD) and examined at mbar pressure by operando sum frequency generation (SFG) spectroscopy and near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) combined with differentially pumped mass spectrometry (MS). ALD enables creating model systems ranging from Pt nanoparticles to bulk-like thin films. Polarization-dependent SFG of CO adsorption reveals both the adsorption configuration and the Pt particle morphology. By combining experimental data with ab initio density functional theory (DFT) calculations, we show that the CO reaction onset is determined by a delicate balance between CO disproportionation (Boudouard reaction) and oxidation. CO disproportionation occurs on low-coordinated Pt sites, but only at high CO coverages and when the remaining C atom is stabilized by a favorable coordination. Thus, under the current conditions, initial CO oxidation is found to be strongly influenced by the removal of carbon deposits formed through disproportionation mechanisms rather than being determined by the CO and oxygen inherent activity. Accordingly, at variance with the general expectation, rough Pt nanoparticles are seemingly less active than smoother Pt films. The applied approach enables bridging both the "materials and pressure gaps".

AB - Pt/ZrO2 model catalysts were prepared by atomic layer deposition (ALD) and examined at mbar pressure by operando sum frequency generation (SFG) spectroscopy and near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) combined with differentially pumped mass spectrometry (MS). ALD enables creating model systems ranging from Pt nanoparticles to bulk-like thin films. Polarization-dependent SFG of CO adsorption reveals both the adsorption configuration and the Pt particle morphology. By combining experimental data with ab initio density functional theory (DFT) calculations, we show that the CO reaction onset is determined by a delicate balance between CO disproportionation (Boudouard reaction) and oxidation. CO disproportionation occurs on low-coordinated Pt sites, but only at high CO coverages and when the remaining C atom is stabilized by a favorable coordination. Thus, under the current conditions, initial CO oxidation is found to be strongly influenced by the removal of carbon deposits formed through disproportionation mechanisms rather than being determined by the CO and oxygen inherent activity. Accordingly, at variance with the general expectation, rough Pt nanoparticles are seemingly less active than smoother Pt films. The applied approach enables bridging both the "materials and pressure gaps".

KW - catalysis

KW - DFT

KW - in situ spectroscopy

KW - NAP-XPS

KW - operando

KW - Pt nanoparticles

KW - SFG

UR - http://www.scopus.com/inward/record.url?scp=85099013602&partnerID=8YFLogxK

U2 - 10.1021/acscatal.0c03974

DO - 10.1021/acscatal.0c03974

M3 - Article

AN - SCOPUS:85099013602

VL - 11.2021

SP - 208

EP - 214

JO - ACS Catalysis

JF - ACS Catalysis

SN - 2155-5435

IS - 1

ER -