Cu Facet-Dependent Elementary Surface Reaction Kinetics of CO₂ Hydrogenation to Methanol Catalyzed by ZrO₂/Cu Inverse Catalysts

Abstract

ZrO2–Cu-based catalysts are active in catalyzing the hydrogenation of CO2 to methanol. Herein, we report Cu facet effects on the catalytic performance of ZrO2/Cu inverse catalysts in CO2 hydrogenation to methanol using various Cu nanocrystals with well-defined Cu morphologies and facets. The ZrO2–Cu interface is the active site, in which the ZrO2–Cu­{100} and ZrO2–Cu­{110} interfaces exhibit similar apparent activation energies of ∼42.6 kJ/mol, smaller than that of the ZrO2–Cu­{111} interface (∼64.5 kJ/mol). Temporal in situ diffuse reflectance infrared Fourier transform spectroscopy characterization results identify the bridge formate hydrogenation as the rate-determining elementary surface reaction under typical reaction temperatures, whose activation energy is similar at the ZrO2–Cu­{100} (∼36.3 kJ/mol) and ZrO2–Cu­{110} (∼40.5 kJ/mol) interfaces and larger at the ZrO2–Cu­{111} interface (∼54.5 kJ/mol). This fundamental understanding suggests Cu facet engineering as a promising strategy to improve the catalytic performance of ZrO2/Cu inverse catalysts for CO2 hydrogenation to methanol.

In Situ Restructuring of ZnCr2O4 Spinel Catalyst Alters Elementary Surface Reaction Kinetics and Catalytic Selectivity in CO Hydrogenation Reaction

“…Meanwhile, previous studies mainly used nonstoichiometric Zn-Cr spinel oxides with excess Zn, which, although catalytically more active than stoichiometric ZnCr 2 O 4 spinel oxide, are less suitable for mechanistic studies due to their more complicate structures. Recently, we successfully used temporal in situ diffuse reflectance infrared Fourier transformed spectroscopy (DRIFTS) to acquire the elementary surface reaction kinetics of working catalysts for unambiguous identifications of the active site–active species pair. − In this work, we combined quasi-in situ X-ray photoelectron spectroscopy (XPS), temperature-programmed reaction spectroscopy (TPRS), and temporal in situ DRIFTS to study the CO hydrogenation reaction catalyzed over a stoichiometric ZnCr 2 O 4 spinel catalyst under working conditions. In situ partial reduction of Zn 2+ in ZnCr 2 O 4 to metallic Zn occurred as the reaction temperature increased from 573 to 673 K, which induced the changes in the elementary surface reaction network and kinetics, particularly for the CH 3 OH formation, and consequently the catalytic selectivity.…”