Molybdenum carbide nanowires as efficient heterogeneous catalyst for CO2 hydrogenation
Date of Issue2016-02-12
School of Chemical and Biomedical Engineering
CO2 hydrogenation is one of the various strategies for CO2 reduction. Molybdenum carbide is one of the heterogeneous catalysts thathave been found catalytically active for CO2hydrogenation. From the open literature, catalytic performance of molybdenum carbide catalyst islinked with their crystal structure. However the characteristic properties of different crystal structures still deserve further investigation. In this research, two main phases of molybdenum carbide catalysts, α-MoC1-x and β-Mo2C were synthesizedfor investigation. The conversion of α-MoC1-x into active α phase was achieved by slightly elevate the carburization temperature from 700℃ to 720℃. The catalytic activity of these molybdenum carbide nanowires materials was assessed in the hydrogenation of CO2. Result showed the apparent activity of active α-MoC1-x catalyst synthesized at 720℃ were 10% higher than β-Mo2C due to its 4 times larger surface area, however the intrinsic activityof active α-MoC1-x catalyst is still lower than β-Mo2C catalyst. With In-situ XPS technique, we discovered the reducibility of β-Mo2C was significantly higher than α-MoC1-x, which corresponded to β-Mo2C catalyst high intrinsic activity. We then conclude the reducibility difference, closely linked to crystal structure difference, and stronglyaffected the catalytic performance. DRIFTS was used to study the adsorption properties of molybdenum carbide nanowires catalyst. We proposed the weak adsorption of CO on molybdenum carbide catalyst explainedcatalyst’s high selectivity behavior.