Insight into the role of metal support interface through the synergistic effect between Ag and α-Bi2Mo3O12 support for the selective oxidation of propylene to acrolein

Abstract

Pre-synthesized morphologically tailored size and shape selective silver nanoparticles (AgNPs) decorated on bismuth molybdate support (AgNPs/α–Bi2Mo3O12) using simple wet impregnation method was employed. The prepared AgNPs/α-Bi2Mo3O12 nanocatalysts were tested in the selective partial oxidation of propylene to acrolein reaction. The introduction of well-defined size and shape of AgNPs on α–Bi2Mo3O12 is greatly promoted the strong metal support interactions (SMSI), creation of oxygen vacancies (Ov) and high propylene adsorption binding energy (calculated by DFT). The strong metal support interactions between Ag and α-Bi2Mo3O12 is clearly elucidated by the high quality HRTEM and STEM–HAADF microscopic images. In addition, surface atomic molar ratio measured by XPS analysis determined the key redox properties of AgNPs/α–Bi2Mo3O12 system and their influence on the overall catalytic efficiency in the oxidation of propylene via reduction of Mo6+ to Mo5+ initiated at low temperatures in Ag/α–Bi2Mo3O12 system. The Mo reduction is further confirmed by the activated oxygen removal from the MoO42– moieties after Ag incorporation on α–Bi2Mo3O12. Thus, confirmed the oxidation reaction pathway follows a Mars–van–Krevelen process. Further, DFT calculations supported the propylene adsorption is more favorable over Ag/α–Bi2Mo3O12 than bare α–Bi2Mo3O12 support. The propylene oxidation performance over Ag/α–Bi2Mo3O12 system was 5.5 times higher than bare α–Bi2Mo3O12 support, probably due to an enabled strong metal support interaction and increased oxygen vacancies.