Real-time dynamics and structures of supported subnanometer catalysts via multiscale simulations

Abstract

Understanding the performance of subnanometer catalysts and how catalyst treatment and exposure to spectroscopic probe molecules change the structure requires accurate structure determination under working conditions. Experiments lack simultaneous temporal and spatial resolution and could alter the structure, and similar challenges hinder first-principles calculations from answering these questions. Here, we introduce a multiscale modeling framework to follow the evolution of subnanometer clusters at experimentally relevant time scales. We demonstrate its feasibility on Pd adsorbed on CeO2(111) at various catalyst loadings, temperatures, and exposures to CO. We show that sintering occurs in seconds even at room temperature and is mainly driven by free energy reduction. It leads to a kinetically (far from equilibrium) frozen ensemble of quasi-two-dimensional structures that CO chemisorption and infrared experiments probe. CO adsorption makes structures flatter and smaller. High temperatures drive very rapid sintering toward larger, stable/metastable equilibrium structures, where CO induces secondary structure changes only.

Kinetic Monte Carlo simulations for heterogeneous catalysis: Fundamentals, current status, and challenges

“…Although, a number of acceleration schemes have appeared in recent years, 87,95,109 further developments are necessary. 38,86,90,91,94,143,144 Along these lines, further improvements in the efficiency of lateral interaction pattern detection, e.g. via fingerprinting and precomputing, could be a way forward.…”

“…120,[292][293][294][295][296] It has also been implemented to study more complex surface reaction systems, such as the selective acetylene hydrogenation over SAA nanoparticles, 297 and oxygen reduction on oxidesupported PtNi nanoalloys. 298 Motivated by the need to understand the performance of subnanometer catalysts and explain how catalyst treatment and exposure to spectroscopic probe molecules change the structure, Wang et al 143 (111) in a CO atmosphere as a case study, since CO is the most common probe molecule in infrared (IR) spectroscopy. 299 The approach gave important insights into the effect of temperature, CO partial pressure, metal loading, and initial catalyst state on cluster formation at that scale.…”

Operando Spectroscopy Unveils the Catalytic Role of Different Palladium Oxidation States in CO Oxidation on Pd/CeO2 Catalysts

“…Nonetheless, typical metal‐oxide catalysts prepared by conventional preparation methods (e.g., impregnation or precipitation) often lack uniformity and contain a mixture of metal nanoparticles, clusters, and single atoms already in the as‐prepared state [7, 29–31] . Moreover, these species can transform into each other depending on the reaction conditions [32–35] . For Pd/CeO 2 , several works demonstrated a coexistence and, in fact, synergy between PdO x clusters and Pd atoms in the CeO 2 lattice for the oxidation of CO at low temperature [36–38] .…”

“…[7,[29][30][31] Moreover, these species can transform into each other depending on the reaction conditions. [32][33][34][35] For Pd/CeO 2 , several works demonstrated a coexistence and, in fact, synergy between PdO x clusters and Pd atoms in the CeO 2 lattice for the oxidation of CO at low temperature. [36][37][38] Other reports stressed the importance of metallic Pd sites for optimal catalytic performance.…”

Titelbild: Operando Spectroscopy Unveils the Catalytic Role of Different Palladium Oxidation States in CO Oxidation on Pd/CeO2 Catalysts (Angew. Chem. 23/2022)

“…[7,[29][30][31] Moreover, these species can transform into each other depending on the reaction conditions. [32][33][34][35] For Pd/CeO 2 , several works demonstrated a coexistence and, in fact, synergy between PdO x clusters and Pd atoms in the CeO 2 lattice for the oxidation of CO at low temperature. [36][37][38] Other reports stressed the importance of metallic Pd sites for optimal catalytic performance.…”