(36h) CO 2 Hydrogenation to Ethanol over Pd/Bi 2 O 3 Catalysts: The Synergisticeffect of Pd Particle Size and Surface Oxygen Vacancy

Efficient conversion of CO 2 reduces its concentration in the atmosphere, providing an alternative resource for the production of fuels and value-added chemicals. Although CO2 conversion has been broadly investigated, the products are generally C1 species. In the present contribution, we demonstrate that CO2 is efficiently converted to ethanol over Pd/Bi2O3 catalysts. A mechanistic study shows that both Pd particle size and the oxygen vacancy synergistically promote ethanol formation from CO2 hydrogenation. It was found that the products of CO2 conversion over Pd/Bi2O3 depend on operating temperatures, Pd particle size and surface oxygen vacancy. We individually investigated these parameters by varying Pd loading amounts (0.1-2.0 wt%), reducing and testing catalysts at different temperatures (200-400 ◦ C). These catalysts were also characterized by BET, TEM, TPO, and TPR. It was found that at 200 and 240 ◦ C, the TOF values (> 0.15 −1 ) of ethanol formation are larger than those under other temperatures (160, 280 and 320 ◦ C). When Pd particle size is 1-1.5 nm, the TOF (0.1-0.2 s −1 ) of ethanol at 200 and 240 ◦ C is relatively high, while when the particle size is larger than 2 nm, the TOF decreases sharply. It indicates that ethanol formation relies on the particle size of Pd. Interestingly, we also found that the oxygen vacancy values and TOF are essentially linearly correlated. These experimental observations propose that CO2 hydrogenation to ethanol over Pd/Bi2O3 catalysts are synergistically promoted by both Pd particle size and surface oxygen vacancy. In conclusion, we show that CO2 is efficiently converted to ethanol over Pd/Bi2O3 catalysts. It was found that small Pd particle size and high oxygen vacancy synergistically promote ethanol formation rate under the investigated operating conditions.