Unraveling Multiscale Kinetics over Subnanometer Cluster Catalysts: H2 Desorption from Pt3(-H)2/γ-Al2O3(110)

Despite the attractiveness of highly dispersed supported metal catalysts due to the efficient usage of the active metal component, the structural complexity of subnanometer metal cluster active sites and the interconnectedness of reaction networks over many active site configurations elude detailed understanding. Here, we perform density functional theory (DFT) calculations and state-based kinetic simulations of the desorption of H2 from Pt3(-H)2 clusters supported on dehydroxylated γ-Al2O3(110), serving as a prototype of such coupled reaction networks. Different from ideal low Miller index metal surfaces and highly symmetric gas-phase clusters, we find many unique H binding sites on the supported Pt3 clusters, resulting in an ensemble of metastable Pt3(-H)2 cluster configurations interwoven within a network of H diffusion, active site restructuring, and H2 desorption elementary steps. Simulations and spectral analysis show that the catalyst and chemistry expose three principal time scales, corresponding to the diffusion of H, restructuring of Pt3(-H)2, and desorption of H2. Free energy span-based interpretations of the reaction pathways and sensitivity analysis of the eigenvalues uncover favorable Pt3(-H)2 restructuring and H2 desorption processes as being kinetically relevant at intermediate and long times. Interestingly, H2 desorption implicates catalyst restructuring as a prerequisite for forming more favorable desorption channels. We introduce simplified ensemble-based models and effective rate constants for the modeling of such multiscale reaction processes.
This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Catalysis, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acscatal.3c02014. This article will be embargoed until August 18, 2024.
supported metal clusters, restructuring, microkinetic modeling, transient kinetics, sensitivity analysis, quasi-equilibrium
Yan, George, and Dionisios G. Vlachos. “Unraveling Multiscale Kinetics over Subnanometer Cluster Catalysts: H2 Desorption from Pt3(-H)2/γ-Al2O3(110).” ACS Catalysis 13, no. 16 (August 18, 2023): 10602–14. https://doi.org/10.1021/acscatal.3c02014.