Can Fluxionality of Subnanometer Cluster Catalysts Solely Cause Non-Arrhenius Behavior in Catalysis?

Abstract

Supported sub-nano clusters are intriguing catalysis, which can present an ensemble of many distinct and easily interconverting geometric states to the reactive medium in catalytic conditions. Each of these states can contribute to catalysis with a unique reaction rate. We argue that such sub-nano cluster catalysts can in principle show a non-Arrhenius behavior, thanks to their structural fluxionality. However, it is unlikely to see this in practice due to the stringent requirements on the heights of the reaction barriers involved. Furthermore, we demonstrate that the ensemble average rate constant which was previously proposed to be used for the ensemble of fluxional clusters to describe the catalytic properties of the system is the same as Tolman's formula proposed in 1920. Note that in this study we only isolate the dynamicity of clusters as one factor that can affect the kinetics of catalysis. We also propose that calculating 1 ! ! (〈 "# 〉 − 〈 $ 〉) as a function of T can be used as a good indicator of a possible non-Arrhenius behavior. instead of (A.7) if we are concerned about the difference between the pre-exponential factor of different isomers in the ensemble. ASSOCIATED CONTENT Plot which shows the Ea,i search space obtained from 40,000 different combinations of Ea,1 and Ea,2 in the range of 0-2 eV for the ensemble of two isomers with different relative energies E1 = 0 and E2 = 0.10, 0.15, 0.20, 0.25, 0.40, and 0.50 eV.

Fluxionality of Subnano Clusters Reshapes the Activity Volcano of Electrocatalysis

“…At finite temperatures, clusters can visit the low‐energy local minima, populating a pool of isomers with distinct structures and reactivities, best represented as a statistical ensemble [5] . In addition, subnano clusters can adapt their shapes and binding sites to bind different adsorbates, causing a breakdown of the scaling relationships (which normally assume consistent binding modes among chemically similar adsorbates), and even potential non‐Arrhenius behavior of reaction kinetics [6,7] …”

A Review of State of the Art in Phosphine Ligated Gold Clusters and Application in Catalysis

“…To calculate for the ensemble of distinct structural isomers, global optimization methodologies, and subsequent Monte Carlo simulations are required. [ 361 ]…”

Dynamics of Heterogeneous Catalytic Processes at Operando Conditions

“…Using the GO technique, they revealed the highly fluxional behavior of Pt 7 over Al 2 O 3 , 75 Cu oxide at a high temperature and different O 2 pressures, 79 and hexagonal boron nitride in the oxidative dehydrogenation of propane. 80 They found that dynamic fluxionality may break the scaling relationships, 81 cause non-Arrhenius behavior, 82 or accelerate the Ostwald ripening of a supported catalyst. 83 Moreover, a bipartite matching algorithm was introduced to connect low-lying isomers obtained from the GO technique and to build the whole picture of the fluxional behavior, 75 as shown in Figure 4 b.…”