The interplay between acid-base properties and Fermi level pinning of a nano dispersed tungsten oxide - titania catalytic system

A series of WO3/TiO2 catalysts were synthesized, characterized, and evaluated for the NO selective catalytic reduction (SCR) with NH3. Based on a wide range of characterization techniques, a detailed model was developed that describes the interfacial electron transfer between WO3 and TiO2 and defines a relationship between the acid-base properties of the catalytic surface and electronic structure modification. The electronic interactions at the WO3/TiO2 interface were quantified using variations in the system's electronic structure. Altering the dispersion and size of the WO3 nanostructures results to drastic changes in titania's surface electron distribution, which are reflected in the pinning of Fermi level through an electron transfer process between WO3 and TiO2. The variations in the Fermi level were further related to changes in the point of zero charge (PZC) values and the activity towards NO SCR with NH3, which was used as a test reaction. Temperature Programmed Surface Reaction (TPSR) was employed to study the catalytic activity at temperatures ranging from 30 C to 500 C and was quantitatively correlated to changes in coverage and interfacial charge transfer. We demonstrate that higher WO3 loading on TiO2 results in a stronger electronic interaction and a higher catalytic activity. This is because electron transfer increases the surface electron density, which enhances the surface basicity of TiO2. The concomitant decrease in the adsorption energy of NH3 results in a decrease in the activation energy, which is reflected in the SCR temperature onset. (c) 2022 Elsevier Inc. All rights reserved.

Automated summary

A series of WO3/TiO2 catalysts were synthesized and characterized for the NO selective catalytic reduction (SCR) with NH3. The interfacial electron transfer between WO3 and TiO2 was studied, and its relationship with the acid-base properties of the catalytic surface and electronic structure modification was defined. The results showed that altering the dispersion and size of the WO3 nanostructures led to changes in titania's surface electron distribution, which affected the catalytic activity. It was found that higher WO3 loading on TiO2 resulted in stronger electronic interaction and higher catalytic activity due to increased surface electron density and enhanced surface basicity.