Understanding the Nature and Activity of Supported Platinum Catalysts for the Water–Gas Shift Reaction: From Metallic Nanoclusters to Alkali-Stabilized Single-Atom Cations

Abstract

Identifying the nature of an active site and understanding the reaction mechanism at the atomic level are of critical importance in the design of efficient catalysts for targeted applications. While extended metal surfaces have been studied extensively for various catalytic processes and relative activities of different metals were predicted using volcano relationships, much less is known with regard to catalysis at metal/oxide interface sites. This Perspective focuses on recent computational studies that were aimed at understanding catalysis at such metal/oxide interface sites. The water–gas shift (WGS) reaction catalyzed by supported Pt catalysts has been chosen as a model system for such an analysis, since extensive computational studies with varying sizes of Pt clusters and supports are available and, thus, by comparison to experimental data, a deeper understanding of the active sites can be attained. Pt catalysts with different sizes and shapes stabilized on various supports were found to be active for the WGS. However, the identification of the exact nature and function of the active site in these catalysts is still a matter of debate. Here, we analyzed the computational studies performed using different active site models, namely, Pt surface models, reducible oxide supported Pt cluster models, and supported single Pt site models. The focus of this Perspective is not to summarize computational or experimental studies of the WGS but to highlight the importance of choosing appropriate active site models and methods in the computational studies such that the experimental behavior of these catalysts and the specific roles of the metal and support can be understood. Furthermore, results obtained for the WGS mechanism catalyzed by Na-stabilized single Pt cations supported on TiO2 are discussed and the promotional role of alkali cations are identified. Finally, we touch upon the importance of uncertainty quantification to account for the inexact nature of DFT in the correlation of computational predictions with experimental observations.

Water Splitting: From Electrode to Green Energy System

“…WGS reaction was a main way for industrial H 2 production [193][194][195][196][197][198][199]. For the traditional WGS reaction, high temperatures and high pressures were essential, and H 2 contamination containing CO 2 , CH 4 and residual CO was inevitable [200][201][202][203][204].…”

Rhodium Single‐Atom Catalysts on Titania for Reverse Water Gas Shift Reaction Explored by First Principles Mechanistic Analysis and Compared to Nanoclusters

“…The size of supported nanoparticles affects catalytic performance for many reactions, such as CO oxidation, [1] methane activation, [2] and CO 2 reduction [3,4] . Taking this size‐dependent catalytic phenomenon to the limit, researchers have been developing atomically dispersed (i. e., single atom) catalysts, which frequently show modified activity and selectivity relative to their larger nanocluster (<2 nm) or nanoparticle counterparts [5–8] . Importantly, atomically dispersed catalysts can also achieve the maximum possible dispersion of metal on a support, making optimal use of rare and expensive metals.…”

Crystal Facet Induced Single‐Atom Pd/CoxOy on a Tunable Metal–Support Interface for Low Temperature Catalytic Oxidation

“…Single‐atom catalysts with lowest limit of minimizing metal nanoparticles for catalytic oxidation, water gas shift, and hydrogenation contain atomic dispersed metal sites and close interactions with the support. [ 1–7 ] Since the metal sites catalyze oxidation reactions and the support sites stabilize O 2 at the interface, the critical properties for single‐atom catalysts lie on the metal–support interface, which is dominated by the variation of the concentration of highly dispersed single atoms. [ 8–12 ] Understanding the phenomena of metal–support interactions is the key to tailor‐made materials.…”