Executive Summary : | Polyoxometalates (POMs) are known for their enhanced photocatalytic activities and electron accepting properties. These materials can also acts as reactive active site for the hydrogen productions. They also contain very high redox potentials and absorb in the visible regions as published by us earlier. These molecular inorganic stabilizers (POMs) will be incorporated at the metal oxide surfaces through covalent linkages which facilitates the charge separation with in the mixed metal oxide-POM hybrids. Here, we will be synthesizing metal oxides TiO2, Fe2O3 and ZnO using hydrothermal synthesis methods. Different sized and shaped mixed metal oxide NPs will be synthesized. Mono, di and tri Lacunary-Keggin and Lacunary Wells-Dawson type polyoxometalates, such as, [PW11O39]5- and [P2W18O62]10- will be used for the preparation of metal oxide and mixed metal-oxide POM hybrid materials under hydrothermal conditions. They also contain very high redox potentials and also they have can absorb in the visible regions as published by us earlier (Angew. Chem. Int. Ed., 2015, 42, 12593, Nature Commun. 2018, 9, 4896 and Angew. Chem. Int. Ed., 2019, 58, 6584). The synthesized NPs will have very high dispersity in water or other solvents. These hybrid materials with metal-oxide NPs, POMs will be used as the reactive photocatalyst, electron storage and reactive site and the visible light photosensitizers respectively. Due to the large charge separation, there will be increased reactivity of the photo-excited hybrids materials. Initial studies suggest that one hybrid photocatalyst can accumulate ~200-300 electrons which will be beneficial to overcome the kinetic barriers. Metal NPs will also be incorporated at the surfaces of these hybrid mixed-metal oxides surfaces to enhance the photocatalytic activity. Metal NPs will act as the reactive surface sites for the formation of H2. Since the photocatalytic water splitting using molecular metal oxide hybrids are still in its nascent stage, the growth of this highly demanding area is inevitable and the scientific outcome of the project will help us to bridge between the traditional heterogeneous photocatalysis with the molecular photocatalysis. We will also study the redox catalysis at oxide/water interfaces depends critically on two fundamental inner-sphere redox steps: proton-coupled electron transfer (PCET). Finally, the proposed studies will also compare the chemistries of inorganic molecular clusters, such as, Keggin-type polyoxometalates (POMs) with different redox ligands and study their role towards the reactivity of NCs. All the ligands will be decorated on the Metal oxide NCs surfaces and their roles of electronic structure, thermochemistry and other parameters on oxide/water interfacial chemistry and catalysis will be studied. A comparative study will be facilitated by the use of colloidal NCs, examining suspensions of similar size NCs in aprotic organic solvents reacting with the same molecular reagents. |
Co-PI: | Dr. Sucheta Sengupta Amity University, Noida, Uttar pradesh,Amity Road, Sector 125, Noida,Uttar Pradesh,Gautam Buddha Nagar-201313 |