Molecular-level insights into the electronic effects in platinum-catalyzed carbon monoxide oxidation

Wenyao Chen,Jia Yang,Zheng Jiang,Gang Qian,Xuezhi Duan,Weikang Yuan,Yueqiang Cao,De Chen,Xinggui Zhou,Hao Zhang,Jing Zhang,Junbo Cao

doi:10.1038/s41467-021-27238-z

Abstract

A molecular-level understanding of how the electronic structure of metal center tunes the catalytic behaviors remains a grand challenge in heterogeneous catalysis. Herein, we report an unconventional kinetics strategy for bridging the microscopic metal electronic structure and the macroscopic steady-state rate for CO oxidation over Pt catalysts. X-ray absorption and photoelectron spectroscopy as well as electron paramagnetic resonance investigations unambiguously reveal the tunable Pt electronic structures with well-designed carbon support surface chemistry. Diminishing the electron density of Pt consolidates the CO-assisted O2 dissociation pathway via the O*-O-C*-O intermediate directly observed by isotopic labeling studies and rationalized by density-functional theory calculations. A combined steady-state isotopic transient kinetic and in situ electronic analyses identifies Pt charge as the kinetics indicators by being closely related to the frequency factor, site coverage, and activation energy. Further incorporation of catalyst structural parameters yields a novel model for quantifying the electronic effects and predicting the catalytic performance. These could serve as a benchmark of catalyst design by a comprehensive kinetics study at the molecular level.

Highlights

A molecular-level understanding of how the electronic structure of metal center tunes the catalytic behaviors remains a grand challenge in heterogeneous catalysis
The types and concentrations of oxygen-containing groups (OCGs) over the carbon nanotubes (CNT) surface vary significantly with the heat treatment temperature owing to their different thermal stabilities, which could be employed as ligands to tailor the electronic properties of metal centers
CO oxidation has been widely studied as a prototypical reaction to elucidate the reaction kinetics for the construction of the electronic structure-surface intermediates-catalytic performance relationship

Summary

Introduction

A molecular-level understanding of how the electronic structure of metal center tunes the catalytic behaviors remains a grand challenge in heterogeneous catalysis. The derived models are based on an abstract and static concept of the “catalyst material”, normally denoted as a free site “*”, giving rise to ambiguous relationships between the microscopic properties of metal sites and the macroscopic catalytic performance[29,30] In this regard, obtaining in situ kinetics information on the adsorption and activation of reaction species, and further combining it with the isotopic studies, characterization results, and theoretical calculations could potentially allow for the bridging of this microscopicto-macroscopic transition. Steady-state isotopic transient kinetic analysis (SSITKA) and in situ XPS measurements were conducted to obtain the kinetics behaviors under operando conditions for kinetics modeling This in situ kinetics strategy for identifying reaction pathways and kinetics indicators to establish the new model could predict the catalytic performance and be extended to the designing of other metal catalysts

Methods

Results

Conclusion