Engineering the surface properties of CeVO4 catalysts to improve low temperature De-NOx performance through regulating pH value in synthesis process

The presence of quick electron transfer in metal oxides can well promote selective catalytic reduction (SCR) of NOx with NH3. Here, a series of CeVO4-X (X = 4, 6, 8, 10 and 12) catalysts with engineering the surface properties were successfully synthesized via controlling pH values in the hydrothermal process. The catalysts were evaluated in the NH3-SCR reaction in the temperature range of 90-420 degrees C. Among them, the CeVO4-8 catalyst with nanorods structure displayed the highest catalytic activity, achieving over 90 % NO conversion between 180 and 390 degrees C. It also showed high N2 selectivity and good tolerance to H2O and SO2. The effect of different pH values on the catalytic activity and microstructure of CeVO4 catalysts was comprehensively characterized using various techniques such as XRD, Raman, SEM, HR-TEM, N2 adsorption-desorption, H2-TPR, O2/ NH3/NO-TPD, XPS, and in-situ DRIFTS. The characterization results revealed that the variation in catalytic activity among these catalysts is attributed to the difference in their surface properties, which were tuned by changing the pH values during synthesis process, despite having the same crystal phase of CeVO4. The superior catalytic performance of the CeVO4-8 catalyst, particularly at low temperature, can be attributed to its higher specific surface area, enhanced acidity, and the electron transfer between cerium and vanadium species (Ce4+ + V4+ <-> Ce3+ + V5+), consequently resulting in increased redox capacity and facilitating the adsorption and activation of NH3 and NO molecules. This study broadens the applications of CeVO4 in the field of low temperature NOx removal.