Promotion effects of oxygen vacancies on activity of Na-doped CeO2 catalysts for reverse water gas shift reaction

Abstract

CeO2-based catalysts have been widely used in the CO2 hydrogenation process. The oxygen vacancies on CeO2 resulted from Na ion incorporation play a vital role in CO2 conversion activity, the effect of Na+ ion-doped in CeO2 during CO2 hydrogenation was rarely studied. In this work, the LN-CeO2 catalysts with different nNaOH:nCe ratios were prepared with liquid nitrogen(Liquid Nitrogen-CeO2, LN-CeO2), and the effect of the nNaOH:nCe ratio on the microstructure of the LN-CeO2 catalysts were evaluated. The best CO2 hydrogenation performance was achieved by LN-CeO2-100 with a CO production rate of 3.90 mol/gcat·h at 800 °C (100% CO selectivity). The kinetic results indicated that the CO2 hydrogenation performance difference among these LN-CeO2 catalysts resulted from the CO2 activation process. Oxygen vacancies could enhance CO2 activation on the surface of LN-CeO2, and oxygen vacancies displayed a linear correlation relationship with the Na content doped in LN-CeO2. The highest concentration of oxygen vacancies resulted from Na ion incorporated and lower CO2 reaction order was closely related to CO2 hydrogenation performance of LN-CeO2-100. These results will give insight into the Na effect on the CO2 hydrogenation mechanism over CeO2.