Insight into the performance of VOx-WOx/TiO2 catalysts modified by various cerium precursors: A combined study on synergistic NOx and chlorobenzene removal

Cerium is widely used as a modifier to enhance the catalytic performance of the selective catalytic reduction (SCR) catalysts due to its exceptional low-temperature properties. However, the effects of different cerium precursors on catalytic performance remains unclear. In this study, VO_x-WO_x/TiO₂ catalysts are modified using Ce(NO₃)₃·6H₂O (cata-N), CeO₂ (cata-O), and Ce(OH)₄ (cata-OH), and their synergistic removal of NO_x and chlorobenzene (CB), as well as their resistance to water and sulfur poisoning, were systematically investigated. Among the tested catalysts, cata-N demonstrated superior CB (45.0-93.3 %) and NO_x (31.9-90.37 %) removal efficiencies under synergistic conditions, along with excellent water resistance (T₉₀ = 193 °C with 5 % H₂O). In contrast, cata-OH exhibited the highest sulfur resistance, maintaining a denitrification efficiency of 20 % after 10 h of sulfur exposure, compared to 9 % for cata-N and 8 % for cata-O. Characterization revealed that Ce(NO₃) ₃·6H₂O improved cerium dispersion, leading to enhanced the redox properties and acidity (especially Brønsted acid sites (BAS)) in cata-N. Density functional theory (DFT) calculations and In-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (In-situ DRIFTS) results revealed that the well-dispersed cerium atoms contributed additional BAS in the form of Ce-OH, while also forming Ti-O-Ce bonds. These Ti-O-Ce bonds facilitated the formation of Ti-OH on the TiO₂ surface. Ti-OH significantly enhanced the adsorption of NH₃ and CB, thereby promoting both the NH₃-SCR and CB oxidation processes. This study offers new insights into the role of cerium precursors and provides a practical strategy for tuning BAS of catalysts in multiple pollutants removal.