Nanostructured Vanadium Oxides for Energy Conversion and Conservation

Increasing worldwide energy consumption has imposed strain on global natural resources. There are a number of sustainable approaches to meeting the energy needs, and many of them can be broadly classified into two main categories: energy conservation and energy conversion. Buildings consume a tremendous portion of the total energy used worldwide, and conserving some of this energy by using technological advancements, such as thermochromic films, holds promise for reducing energy footprints. There is also an urgent need to tap into renewable sources of energy. Solar energy, if harvested and stored appropriately, could easily meet the energy needs of the world’s population. One route to solar energy conversion involves conversion of solar energy to chemical energy by splitting water to produce hydrogen and oxygen; hydrogen could then be stored and combusted to release the energy. Unfortunately, this has been a challenge for the scientific community since it requires the concerted transfer of four holes and four electrons. In this work, we explore the use of vanadium oxides for both energy conservation and energy conversion applications. First, for energy conservation, vanadium dioxide (VO2) has been explored for use within a dynamically switchable thermochromic thin film. VO2 is able to block infrared light at high temperatures while allowing it to transmit at lower temperatures. Amorphous silica shells have been constituted around VO2 nanowires using a modified Stӧber method in order to embed these films onto a glass matrix. By controlling particle size, it is possible to achieve significant modulation of near-infrared wavelengths of the electromagnetic spectrum. Addressing energy conversion, a tunable platform has been developed with the intent of harvesting solar energy. Heterostructures linking CdSe/β-PbxV2O5 and CdS/β-PbxV2O5 have been synthesized through two different methods, linker-assisted assembly and successive ionic layer adsorption and reaction. Hard X-ray photoelectron spectroscopy and transient absorption spectroscopy studies show thermodynamic alignment of the energy levels and suggest hole transfer from the photoexcited semiconductor quantum dots to the mid-gap states of β-PbxV2O5. The CdS heterostructures show an improved alignment of their valence band with the mid-gap state of β-PbxV2O5. The tunable heterostructure platform holds promise for water splitting photocatalysts

Nanostructured Vanadium Oxides for Energy Conversion and Conservation

Increasing worldwide energy consumption has imposed strain on global natural resources. There are a number of sustainable approaches to meeting the energy needs, and many of them can be broadly classified into two main categories: energy conservation and energy conversion. Buildings consume a tremendous portion of the total energy used worldwide, and conserving some of this energy by using technological advancements, such as thermochromic films, holds promise for reducing energy footprints. There is also an urgent need to tap into renewable sources of energy. Solar energy, if harvested and stored appropriately, could easily meet the energy needs of the world’s population. One route to solar energy conversion involves conversion of solar energy to chemical energy by splitting water to produce hydrogen and oxygen; hydrogen could then be stored and combusted to release the energy. Unfortunately, this has been a challenge for the scientific community since it requires the concerted transfer of four holes and four electrons. In this work, we explore the use of vanadium oxides for both energy conservation and energy conversion applications. First, for energy conservation, vanadium dioxide (VO2) has been explored for use within a dynamically switchable thermochromic thin film. VO2 is able to block infrared light at high temperatures while allowing it to transmit at lower temperatures. Amorphous silica shells have been constituted around VO2 nanowires using a modified Stӧber method in order to embed these films onto a glass matrix. By controlling particle size, it is possible to achieve significant modulation of near-infrared wavelengths of the electromagnetic spectrum. Addressing energy conversion, a tunable platform has been developed with the intent of harvesting solar energy. Heterostructures linking CdSe/β-PbxV2O5 and CdS/β-PbxV2O5 have been synthesized through two different methods, linker-assisted assembly and successive ionic layer adsorption and reaction. Hard X-ray photoelectron spectroscopy and transient absorption spectroscopy studies show thermodynamic alignment of the energy levels and suggest hole transfer from the photoexcited semiconductor quantum dots to the mid-gap states of β-PbxV2O5. The CdS heterostructures show an improved alignment of their valence band with the mid-gap state of β-PbxV2O5. The tunable heterostructure platform holds promise for water splitting photocatalysts