Direct Evidence of Dynamic Metal Support Interactions in Co/TiO2 Catalysts by Near-Ambient Pressure X-ray Photoelectron Spectroscopy

Abstract

The interaction between metal particles and the oxide support, the so-called metal–support interaction, plays a critical role in the performance of heterogenous catalysts. Probing the dynamic evolution of these interactions under reactive gas atmospheres is crucial to comprehending the structure–performance relationship and eventually designing new catalysts with enhanced properties. Cobalt supported on TiO2 (Co/TiO2) is an industrially relevant catalyst applied in Fischer−Tropsch synthesis. Although it is widely acknowledged that Co/TiO2 is restructured during the reaction process, little is known about the impact of the specific gas phase environment at the material’s surface. The combination of soft and hard X-ray photoemission spectroscopies are used to investigate in situ Co particles supported on pure and NaBH4-modified TiO2 under H2, O2, and CO2:H2 gas atmospheres. The combination of soft and hard X-ray photoemission methods, which allows for simultaneous probing of the chemical composition of surface and subsurface layers, is one of the study’s unique features. It is shown that under H2, cobalt particles are encapsulated below a stoichiometric TiO2 layer. This arrangement is preserved under CO2 hydrogenation conditions (i.e., CO2:H2), but changes rapidly upon exposure to O2. The pretreatment of the TiO2 support with NaBH4 affects the surface mobility and prevents TiO2 spillover onto Co particles.

Unveiling Key Interface Characteristics of Ni/Yttria-Stabilized Zirconia Solid Oxide Cell Electrodes in H2O Electroreduction Using Operando X-ray Photoelectron Spectroscopy

“…The ISISS is a bending magnet based-beamline dedicated to soft X-ray photoemission spectroscopy at photon energies between 200 and 1500 eV, as described elsewhere . The CAT branch of the dual-color Energy Materials In Situ Laboratory (EMIL) beamline (CAT@EMIL) , provides access to both soft and hard (in this case 4.9 keV, which is in the border between hard and tender X-ray regime) X-ray radiation. Both experimental stations are equipped with a SPECS PHOIBOS 150 NAP hemispherical energy analyzer with a 2D-CMOS detector.…”

Deciphering Local Structural Complexity in Zn/Ga-ZrO2 CO2 Hydrogenation Catalysts

“…Following the challenge of high-impact CO 2 conversion, several research groups are investing massive effort in the development of new catalysts capable of converting carbon dioxide into high-value products such as CH 3 OH, formaldehyde, methane, hydrocarbons, and olefins. − For future industrial application, the developed catalysts are required to withstand high-temperature and high-pressure conditions, often in a steam-rich environment. These harsh conditions are also associated with the presence of an acidic zeolite/zeotype in the case of tandem catalysts for the direct conversion of CO 2 to hydrocarbons. − The common denominator of these studies is to find the right combination of guest atom and concentration that leads to higher catalytic activity, which often implies a systematic trial-and-error approach by screening several elements.…”