Improved NH3-SCR activity by the cooperation of FeVO4 and CeO2 nanosheet catalysts: structure and mechanism

A series of FeVO4/CeO2 nanosheet catalysts featuring various mass percentages (x%) of FeVO4 (denoted x%FeV/CeO2-S) were synthesized and employed in selective catalytic reduction (SCR) of NOx with NH3. Among them, 10%FeV/CeO2-S exhibited the optimal NH3-SCR activity, achieving over 90% NOx conversion and more than 98% N-2 selectivity at 216-365 & DEG;C, while 10%FeV/CeO2-P catalyst prepared by loading FeVO4 on CeO2 nanoparticles showed over 90% NOx conversion and above 96% N-2 selectivity at 272-345 & DEG;C. The combination of FeVO4 with CeO2 nanosheets was superior to that with CeO2 nanoparticles, which significantly improved the NH3-SCR activity of the catalyst at low and medium temperatures and broadened the operating temperature window. CeO2 nanosheets interacted with FeVO4 stronger than with CeO2 nanoparticles, which was conducive to the dispersion of FeVO4, inhibited the grain growth of CeO2 nanosheets, and improved the ratios of lattice defects, Ce3+ and oxygen vacancies. Moreover, the morphology of the nanosheets was conducive to the electron transfer between Ce, Fe and V. These finally enhanced the surface acidity and redox ability of the FeVO4/CeO2 nanosheet catalysts. As the mass percentage of FeVO4 increased, it tended to gather on the surface of CeO2 nanosheets, which weakened the interaction between them. When the mass percentage of FeVO4 increased to 20%, the specific surface area and the surface acidity decreased greatly, leading to a significant decline in NH3-SCR activity. Furthermore, the coexistence of Eley-Rideal and Langmuir-Hinshelwood mechanisms was observed on the 10%FeV/CeO2-S catalyst.