Design of Transition Metal Oxide and Phosphide Nanomaterials: Their Catalytic Activities

This thesis is focused on developing transition metal-based oxide and phosphide nanomaterials for catalytic application in energy conversion and the organic transformation reaction. The research projects presented in this thesis are: (1) the design and synthesis of transition metal doped ZnO catalysts for the oxygen reduction reaction (ORR), (2) the development of mesoporous FeP and CoP materials as hydrogen evolution reaction (HER) catalysts for electrochemical water splitting, and (3) the fabrication of different ZnO morphologies for coumarin synthesis by the Knoevenagel condensation. The first chapter describes the significance and background of the three research projects. We emphasize the current challenges in developing HER and ORR catalysts for water electrolysis and fuel cell application. Additionally, the importance of coumarins and challenges in their synthesis via the Knoevenagel condensation is included in this chapter. The second chapter contains the synthesis and characterization of transition metal (Mn, Fe, Co, and Ni) doped ZnO nanocrystals. The goal of this study is to develop ZnO based low-cost ORR catalysts. Single-doped and multi-doped transition-metal ZnO samples are synthesized to investigate the effects of doping in the ZnO structure and their activities for ORR. The ORR activity of the ZnO samples is governed primarily by the oxygen vacancies created as a result of the incorporation of dopant elements. The third chapter is comprised of developing mesoporous FeP and CoP nanomaterials as an efficient HER catalyst. A noble approach, the inverse micelle sol-gel method, is utilized to synthesize mesoporous FeP, Co-FeP, CoP, Ni-CoP, and Ni-CoP/CNT materials. The mesoporosity and HER activity of the materials are monitored with the dopants and CNT support. The HER activity of the catalysts predominantly alters with the charge-transfer capabilities of the materials. The fourth chapter includes the preparation of different ZnO morphologies as catalysts for coumarin synthesis. The ZnO properties of different morphologies and their catalytic activities for coumarin synthesis by the Knoevenagel condensation reaction are examined. Catalysts synthesized using methanol show the highest activity. The enhanced activity of the ZnO synthesized in methanol is attributed to the combined effects of relatively high surface area, pore volume, and pore sizes of the materials