Date of Award
Master of Science (MS)
Dr. Ahmed Alzamly
Dr. Soleiman Hisaindee
Dr. Ihsan Ahmed
The production of value-added products through CO₂ utilization using photocatalysis offers an alternative green route for CO₂ fixation. Wide bandgap photocatalysts allow the absorption of light in the UV region, which represents the lowest percentage of the sunlight irradiation. On the other hand, narrow bandgap photocatalysts absorb light in the visible region, though the recombination rate of the generated electron-hole pairs affects their activity. In this thesis, the narrow band gap FeNbO₄ is synthesized, studied and efforts are made to reduce the recombination rate and enhancing the photocatalytic activity.
FeNbO₄ visible-light-driven photocatalysts are synthesized using various synthetic methods and different pH values and characterized using UV-vis DRS, PXRD, BET, SEM, and EDS. Monoclinic phase is obtained for all different preparation methods, where band gap and surface area varied with synthesizing method and pH value. FeNbO₄prepared via co-precipitation method presented the highest surface area with a band gap value of 1.85 eV.
FeNbO₄ prepared via co-precipitation method is further synthesized incorporating rGO. Three different mass ratios of rGO were used, FeNbO₄-3% rGO, FeNbO₄-5% rGO, and FeNbO₄-10% rGO. Results confirm the successful incorporation of rGO into FeNbO₄ and the role of rGO in reducing the recombination rate. The prepared composites are examined for the photocatalytic cycloaddition of CO₂ into propylene oxide, where FeNbO₄-5% rGO exhibits the highest photocatalytic activity with a percent yield of 57%.
Moreover, three FeNbO₄/NH₂-MIL-125(Ti) composites with different mole ratios are prepared, characterized and their photocatalytic activity is evaluated for the same reaction. Obtained data confirms that the reaction proceeds photocatalytically. FeNbO₄ (75%) /NH₂-MIL-125(Ti) (25%) shows the highest percent yield of 52%, results suggest the cooperative mechanism between FeNbO₄ and NH₂-MIL-125(Ti).
Both composites FeNbO₄/rGO and FeNbO₄/NH₂-MIL-125(Ti) have proven to be effective in increasing photocatalytic activity compared to FeNbO₄. As percentage rGO increases, the photocatalytic activity has increased showing the highest yield for FeNbO₄-5% rGO where rGO works as electron trapper, hindering electron-hole pairs recombination. The high percent yield obtained for FeNbO₄ (75%) /NH₂-MIL-125(Ti) (25%)is related to the capability of FeNbO₄ to absorb more light generating electronsthat move to the(LUMO) of NH₂-MIL-125(Ti), hence reducing therecombinationrate. Future work could be directed toward testing various epoxidessubstrate tocompare the effectivenessofthephotocatalysts. Furthermore, differentsynthesizingmethods forpreparing composites could be implemented to enhance the interaction ofboth systems thus improving the photoactivity ofthe photocatalysts.
Hussein Ahmed, Salwa Abdelrahim, "Synthesis, Characterization, Electronic Structure of Reduced Graphene Oxide Modified FeNbO₄, NH₂-Mil-125(Ti) Modified FeNbO₄ Composites and Their Photo catalytic Activities" (2020). Chemistry Theses. 12.