Below-Room-Temperature C–H Bond Breaking on an Inexpensive Metal Oxide: Methanol to Formaldehyde on CeO₂(111)

Abstract

Upgrading of primary alcohols by C-H bond breaking currently requires temperatures of >200 °C. In this work, new understanding from simulation of a temperature-programmed reaction study with methanol over a CeO(111) surface shows C-H bond breaking and the subsequent desorption of formaldehyde, even below room temperature. This is of particular interest because CeO is a naturally abundant and inexpensive metal oxide. We combine density functional theory and kinetic Monte Carlo methods to show that the low-temperature C-H bond breaking occurs via disproportionation of adjacent methoxy species. We further show from calculations that the same transition state with comparable activation energy exists for other primary alcohols; with ethanol, 1-propanol, and 1-butanol explicitly calculated. These findings indicate a promising class of transition states to search for in seeking low-temperature C-H bond breaking over inexpensive oxides.

DFT Study of Methanol Adsorption on Defect‐Free CeO2 Low‐Index Surfaces

“…The low‐temperature catalytic decomposition of methanol for the production of hydrogen offers a promising solution for the replacement of fossil fuels; this process has potential for low cost and high efficiency compared with the high‐temperature steam reforming process that is commonly used at present . Considerable work has been done on a range of materials in the search for suitable catalysts, including noble metals, metal oxides, and composites of the two .…”

CheKiPEUQ Intro 1: Bayesian Parameter Estimation Considering Uncertainty or Error from both Experiments and Theory**

“…Temperature programmed reactions (including temperature programmed desorption) are transient kinetics experiments and are often utilized to try to gain insight into the mechanisms and kinetics of surface reactions. Studies investigating transient kinetics through use of differential equations to simulate the rates and concentrations across time can be useful for obtaining kinetic parameters for complex reaction networks (including for cases where there are coverage dependent activation energies) [8,83–97] …”

Synthesis, Structure and Catalytic Properties of Faceted Oxide Crystals

“…More broadly, the deleterious effect of OVs on formaldehyde selectivity during methanol dehydrogenation over CeO 2 surfaces has not been sufficiently well‐explained. Possible explanations include the role of vacancies in facilitating C−O or C−H bond cleavage, poisoning of vacancies by formaldehyde, or the transfer of hydrogen from methoxy groups associated with vacancies to those that are not, as recently proposed by Sutton et al [281] …”

“…More broadly, the deleterious effect of OVs on formaldehyde selectivity during methanol dehydrogenation over CeO 2 surfaces has not been sufficiently well-explained. Possible explanations include the role of vacancies in facilitating CÀ O or CÀ H bond cleavage, poisoning of vacancies by formaldehyde, or the transfer of hydrogen from methoxy groups associated with vacancies to those that are not, as recently proposed by Sutton et al [281] Unlike the case of CO oxidation, selectivity and rate differences in methanol dehydrogenation have not been explored extensively from the standpoint of adspecies as a function of crystal habit. An exception is the study by Overbury and coworkers quantifying different types of methoxy species on CeO 2 octahedra, cubes, and nanorods using IR and Raman spectroscopy.…”