Growth of stable surface oxides on Pt(111) at near-ambient pressures
Summary¶
Fantauzzi et al. combine near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) with ReaxFF grand-canonical Monte Carlo (ReaxFF-GCMC) to study oxidation of Pt(111) under oxygen at pressures and temperatures representative of catalytic environments, rather than ultra-high vacuum (UHV) reference states alone. Experiments show that oxide formation can require hours even when thermodynamics would suggest facile oxidation, underscoring a kinetic bottleneck that UHV-focused narratives may underemphasize. ReaxFF-GCMC samples oxygen chemical potential-driven insertion/deletion moves using ReaxFF energies to explore disordered surface oxide films that are difficult to treat with DFT for large amorphous supercells. Adri C. T. van Duin appears among authors, linking the study to the group’s Pt–O reactive parameterization line and operando-adjacent modeling culture.
Methods¶
A — Force-field training / fitting: ReaxFF for Pt–O surface chemistry is used as an existing parametrization suitable for oxygen insertion energetics in GCMC; the article does not center on refitting bond parameters in this work.
B — Molecular dynamics / sampling: ReaxFF grand-canonical Monte Carlo (ReaxFF-GCMC) samples oxygen insertion/deletion at fixed temperature and oxygen chemical potential, evaluating configurations with ReaxFF to explore disordered/amorphous surface oxide films (T = 430–680 K, \(p(\mathrm{O}_2)=1\ \mathrm{mbar}\) per abstract-level summary). This is thermodynamic sampling rather than long-time MD growth kinetics.
C — DFT / static QM: Not used as the primary large-cell enumerator—DFT cost for disordered oxides motivates ReaxFF-GCMC; any DFT in the paper is supporting comparison (see full PDF).
D — Review / non-simulation framing: Experiment: near-ambient pressure XPS (NAP-XPS) follows Pt(111) oxidation over hour timescales under O\(_2\) above UHV—paired with simulation for coverage/trend interpretation.
Atomistic sampling note (vs production MD). The simulation layer is ReaxFF grand-canonical Monte Carlo (ReaxFF-GCMC), i.e. Monte Carlo moves in oxygen chemical potential space evaluated with ReaxFF, not a long MD trajectory. Engine / code: ReaxFF-GCMC as reported in the article (implementation details in SI/PDF). System: Pt(111) surface oxide motifs; supercell sizes and O coverage grids are in the full text. Boundaries / periodicity: N/A — explicit PBC statements are not copied into this short wiki summary (see PDF). Ensemble / timestep / thermostat / barostat: N/A — GCMC has no fs integration timestep or NVT/NPT thermostat in the sense of MD; treat equilibration of the GCMC chain as described in-source. Duration / staging: NAP-XPS tracks hour-scale oxidation transients; GCMC sampling duration is reported in MC statistics in the article, not as ps/ns MD. Temperature: 430–680 K window quoted in the abstract for the GCMC conditions paired with experiment. Pressure / gas: \(p(\mathrm{O}_2)=1\ \mathrm{mbar}\) in the abstract-level summary. Electric field: N/A — not used. Replica / enhanced sampling: N/A — GCMC is already a statistical sampling method rather than umbrella/metadynamics.
Findings¶
Kinetics: Surface oxides develop on hour timescales under the experimental conditions, slower than naive extrapolation from many UHV experiments would suggest. Structure: GCMC with ReaxFF identifies stable amorphous surface oxides in the targeted temperature/pressure window, a regime where DFT faces cell-size limits for disordered phases. Consistency: Simulated coverages and qualitative trends align with NAP-XPS observations, supporting the joint experiment + reactive simulation interpretation.
Limitations¶
GCMC emphasizes equilibrium sampling; full growth kinetics may require MD or kinetic Monte Carlo extensions. Language/edition differences between Angew. PDFs should be checked at the DOI. NAP-XPS timescales are experimental observables; mapping them to GCMC equilibria is interpretive and should cite both methods’ assumptions.
Reader notes (navigation)¶
- Galley duplicate: 2017fantauzzi-venue-untitled-2.
- For retrieval, pair this entry with operando catalysis hubs and with Pt surface pages; avoid conflating oxide thermodynamics with electrochemical polarization unless the source text supports it.
Relevance to group¶
van Duin-parameter ReaxFF coupled to GCMC for Pt oxidation under realistic gas pressures—strong catalysis link.