Study Of Photo-thermal Synergistic Catalytic CO₂ Hydrogenation & The Impact On Catalytic Activity Results From Introducing G-C₃N₄-ZnO As Support

The CO2 hydrogenation is a reaction received much focus in the background of increasingly serious green-house effect as the reaction has the potential of converting excessive CO2 into the highly important industrial feedstock methanol.It is seen as a solution to the green-house effect and the incoming fossil fuel shortage.However,this reaction currently is far away from large scale industrial application for the two following reasons:1.The technology of H2 production is still too expensive to make CO2 hydrogenation cost-effective.2.The low CO2 conversion rate and the requirement for harsh condition to get an applicable methanol selectivity.To get a higher CO2 conversion rate,we innovatively introduced light irradiation into the traditional fix-bed reactor to further promote CO2 hydrogenation.According to our research,we found that CO2 conversion in the photo-thermal catalytic condition increase significantly achieving a higher CO2 conversion rate in lower pressure(1.2MPa).To find out the mechanism behind the promotion,we carried out series of control experiments and characterizations.Through analyzing the results,we came out a mechanism with the idea centering on light irradiation promotes Pd metal part of catalyst to interact with its support thereby creating more efficient active sites.Then we tried to go further with the idea by introducing narrow band-gap semiconductor into ZnO to form heterojunction within the support of catalyst.The second part of experiments in the thesis is about exploring the mechanism of our finding in the previous part that catalyst with the support of g-C3N4-ZnO gives higher methanol yield in CO2 hydrogenation.Through characterizations to unravel the electronic properties of the modified catalysts,we purposed it is the g-C3N4 makes the ZnO part of catalyst more electron-rich and thus more reducible.And the partly reduced ZnO,spontaneously wets the surface of the metallic Cu creating more Cu/ZnOx interface.And the Cu/ZnOx interface has been proven by DFT calculations in literatures to be crucial in stabilizing the intermediates of methanol synthesis.