Origin of Thermal and Hyperthermal CO₂ from CO Oxidation on Pt Surfaces: The Role of Post‐Transition‐State Dynamics, Active Sites, and Chemisorbed CO₂

Abstract

The post-transition-state dynamics in CO oxidation on Pt surfaces are investigated using DFT-based ab initio molecular dynamics simulations.While the initial CO 2 formed on at errace site on Pt(111) desorbs directly,i ti st emporarily trapped in ac hemisorption well on aP t(332) step site.T hese two reaction channels thus produce CO 2 with hyperthermal and thermal velocities with drastically different angular distributions,i na greement with recent experiments (Nature, 2018,5 58, 280-283). The chemisorbed CO 2 is formed by electron transfer from the metal to the adsorbate,r esulting in ab ent geometry.W hile chemisorbed CO 2 on Pt(111) is unstable,i ti ss table by 0.2 eV on aP t(332) step site.T his helps explain why newly formed CO 2 produced at step sites desorbs with far lower translational energies than those formed at terraces.This work shows that steps and other defects could be potentially important in finding optimal conditions for the chemical activation and dissociation of CO 2 .

Steric Effects in CO Oxidation on Pt(111) by Impinging Oxygen Atoms Lead to an Exclusive Hot Atom Mechanism

“…Although the calculations show CO molecule prefers to adsorb on face-centered cubic site (fcc), which is known as the “CO/Pt(111) puzzle” in the literature, the CO molecule was set to adsorb on top site in this work to be consistent with experimental observations . The CO adsorption energy at the top site was calculated to be −1.64 eV, which is in good agreement with both previous experimental and theoretical values. , The energy difference between the fcc and top sites is not large (0.12 eV), and the CO molecule is stable at the top site. On the other hand, the O atom prefers to adsorb on the fcc site, with an adsorption energy of −4.67 eV.…”

“…60 The CO adsorption energy at the top site was calculated to be −1.64 eV, which is in good agreement with both previous experimental and theoretical values. 58,61 The energy difference between the fcc and top sites is not large (0.12 eV), and the CO molecule is stable at the top site. On the other hand, the O atom prefers to adsorb on the fcc site, with an adsorption energy of −4.67 eV.…”

Neural Network Representations for Studying Gas‐Surface Reaction Dynamics: Beyond the Born‐Oppenheimer Static Surface Approximation†

“…[ 4‐6 ] Recent experiments show that recombinative desorption could be also non‐ thermal and strongly influenced by post‐transition state dynamics. [ 7‐8 ] In general, the interaction time between the impinging species and the surface is often short enough so that the intramolecular vibrational redistribution (IVR) is incomplete and the energy flow among the molecular and surface degrees of freedom (DOFs) is nonstatisical. [ 9 ]…”

Dynamics Studies of O2 Collision on Pt(111) Using a Global Potential Energy Surface

“…In the previous calculations, , the potential energies of TBMD were approximated by a tight-binding Hamiltonian, and ReaxFF PES was parameterized and fitted by a database of pre-computed DFT energies, both of which may introduce an error of roughly 0.2 eV diverged from DFT values. The AIMD approach computes the motion of all atoms and potential energies on the fly and enables a rather accurate description of both interaction and energy exchange between the impinging molecule and surface. , However, AIMD requires a large number of DFT calculations, making it computationally expensive, and only a small number of AIMD trajectories is affordable, making a good statistical sampling difficult. , Recently, neural network (NN) methods have been widely used for fitting high-dimensional ab initio PES because of flexible nonlinear analytical functions which can represent a multidimensional data set with high fidelity. − The permutation invariant polynomial-NN (PIP-NN) approach incorporates both the permutation symmetry of the molecule and surface periodicity in the NN method that has achieved great success in representing high-dimensional PESs for interactions between various molecules and surfaces. − To the best of our knowledge, there has been no global DFT PES reported for the O 2 /Pt­(111) system, which is undoubtedly desirable for a better understanding of the sticking mechanisms. Here, we present the first six-dimensional PES constructed with thousands of DFT energies based on the Born–Oppenheimer and static surface (BOSS) approximation .…”