Prediction of morphological changes of catalyst materials under reaction conditions by combined ab initio thermodynamics and microkinetic modelling

Abstract

Microkinetic modeling, ab initio thermodynamics and Wulff–Kaishew construction are used to predict catalyst structural changes under reaction conditions.

Enumerating Active Sites on Metal Nanoparticles: Understanding the Size Dependence of Cobalt Particles for CO Dissociation

“…In all cases, the RDFs correspond to those expected for a bulk phase composed of fcc and hcp crystalline cobalt, which is consistent with the X-ray diffraction (XRD) patterns of practical cobalt catalysts. 21 , 30 The influence of faster cooling on the obtained geometries is exemplified for a 4.5 nm cobalt nanoparticle in Figure S3 (Supporting Information). Too fast cooling leads to an amorphous bulk structure, while a preference for an fcc bulk structure develops when the annealing trajectories are not long enough.…”

“…Although the often used Wulff theorem can be used for dispersion calculations, it suffers from the limitations that edge and corner effects should be neglected so that the outcome is the only representative for particles much larger than the typical sizes at which strong structure sensitivity is observed in experiments. 21 In Wulff construction and lattice models, it is also assumed that nanoparticles are monocrystalline, while, in practice, metal nanoparticles can be polycrystalline. 22 To remedy this, we demonstrate a general procedure based on a force field trained from DFT data for optimizing the geometry of nanoparticles without initially imposing any crystal structure.…”

Understanding effects of Ni particle size on steam methane reforming activity by combined experimental and theoretical analysis

“…is neglected. However, in the real reaction, the catalyst might modify its morphology [63], possibly leading to the change of activity as well as effective activation energy. In addition, possible contributions of the support to the reaction, such as water activation was not considered in the model.…”

“…The method developed here can be expected to rationalize the effect of support on the particle shapes and possible change in shape of particles during reactions. It has been recently reported by Maestri and coworkers [63] that the morphology of Rh/α-Al2O3 changed with reaction conditions in catalytic partial oxidation of methane by using combined Wulff-Kaishew construction, ab initio thermodynamics and microkinetic modeling. The change in particle shape resulted mainly in the change in fraction of different facets, thus the changes in the activity.…”

Surface Chemistry of Carbon Dioxide on Copper Model Catalysts Studied by Ambient-Pressure X-ray Photoelectron Spectroscopy

“…Operando observation of morphology and surface structure of catalysts during reaction is another important research topic since they can be affected by reaction environment, e.g. gas composition, pressure, and temperature [21,22]. Atomic force microscopy (AFM) [23,24] and scanning tunneling microscopy (STM) [25−27] are widely used for atomic-scale measurements of surface structures under reaction conditions.…”