DOI: 10.5061/dryad.x3ffbg7vb
title: Cooperative O-atom binding produces the active configuration for OH formation in high-temperature catalytic hydrogen oxidation

description: Much effort in heterogeneous catalysis has gone into identifying “active
 sites” responsible for reactivity, knowledge of which could make
 predictive first principles theories useful for rational catalyst design.
 A major challenge arises since the structures that account for catalytic
 acceleration of reactivity may only form while reacting at high
 temperatures and pressures. This makes experimental tools that have proven
 useful in identifying active sites in ultrahigh vacuum and at low
 temperature of dubious utility. In this work, we present velocity-resolved
 kinetics (VRK) measurements for catalytic hydrogen oxidation on Pd over a
 wide range of surface concentrations and at high temperatures. The rates
 exhibit a complex dependence on oxygen coverage and step density, which
 can only be explained by a kinetic model derived from density functional
 theory (DFT) used in combination with transition-state theory (TST), when
 one includes a cooperatively stabilized configuration of at least three
 O-atoms at steps. Here, two O-atoms recruit a third O-atom to a nearby
 binding site, to produce an active configuration of reactants that is far
 more reactive. Thus, hydrogen oxidation on Pd reveals a clear example of
 how reactivity can be enhanced on a working catalyst. We speculate that
 such active configurations formed by cooperative adsorbate binding play an
 important role in many real-world catalytic processes.
description: # Cooperative O-atom binding produces the active configuration for OH
 formation in high-temperature catalytic hydrogen oxidation
 [https://doi.org/10.5061/dryad.x3ffbg7vb](https://doi.org/10.5061/dryad.x3ffbg7vb) ## Description of the data and file structure Two zip files are provided here. The file named 'dft_structures' contains geometry files of the structures given in the supplementary information (SI) of the paper. The files are named after the nomenclature used in the SI (S1 to S29). The file named 'experimental_data' contains the kinetic traces aquired in this work. Four folders are provided containing data for Pd(332) and Pd(111)  under oxygen rich and oxygen lean conditions. ### Files and variables #### File: dft\_structures.zip **Description:** The file named 'dft_structures.zip' contains geometry files of the structures given in the supplementary information (SI) of the paper. The files are named after the nomenclature used in the SI (S1 to S29). #### File: experimental\_data.zip **Description:** The file named 'experimental_data.zip' contains the kinetic traces aquired in this work. Four folders are provided containing data for Pd(332) and Pd(111)  under oxygen rich and oxygen lean conditions. In the following, the file naming is explained for oxygen rich conditions (A) as well as for oxygen lean conditions (B), followed by general information (C). (A): An example file Name for Oxygen rich conditions is explained in the following: Eample file path: oxygen_rich_Pd332/H2O-Kin-80C-50H2-250O2.dat Explanations: oxygen_rich_Pd332: In the oxygen rich Experiments, a pulse of H2 triggers the reaction on an Oxygen covered surface as explained in sec. S1 of the SI. H2O: the measured species was water (mass 18) Kin: the measurement is a kinetic trace 80C: the Surface temperature in Celsius 50H2: the Repetition rate of the H2 nozzle 250O2: the Repetition rate of the O2 nozzle. The resulting steady state O-Atom Coverage is presented in sec. S1.1. of the SI. (B): An example file Name for Oxygen lean conditions is explained in the following: Eample file path: oxygen_lean_Pd332/Kin-H2O-225C-10O2-7p10em7H2-unten.dat oxygen_lean_Pd332: In the oxygen lean Experiments, a pulse of O2 triggers the reaction on a H-atom covered surface as explained in sec. S1 of the SI. H2O: the measured species was water (mass 18) Kin: the measurement is a kinetic trace 225C: the Surface temperature in Celsius 10O2: the Repetition rate of the O2 nozzle 7p10em7H2: 7.10x10^-7 mbar. The Static Background pressure of H2 in the chamber due to leaking in H2 gas, read by an ion gauge calibrated for N2 gas. The number has to be multiplied by 2.4 to obtain H2 pressure. The conversion from H2 pressure to H-atom coverage is given in sec. S3 of the SI. (C): All files from experimental_data.zip contain two columns, where the first column is time in Micro seconds and the second column is water flux in arbitrary Units ## Code/software The vasp files can be viewed by many free structure visualization programs such as VESTA. The kinetic traces are text files and can be viewed by any editor.