(199b) Semiconducting Heterostructures for Photocatalytic Reduction of Carbon Dioxide

The current environmental and energy scenario demands significant interest in renewable energy. With decreasing fossil fuel resources globally and increased concern over energy security, harvesting solar energy seems imperative. The environmental concerns are mainly due to the rising carbon dioxide levels in the atmosphere. Hence a rational solution to this problem is to convert waste CO₂ to hydrocarbons using solar energy. Amongst the different routes to achieve this purpose, solar photocatalytic conversion has garnered a lot of interest. Photocatalytic processes are associated with advantages of low temperature reactions. Moreover the prospect of utilizing the abundant solar energy to convert CO₂ to any useful hydrocarbon is appealing. A majority of the photocatalysts being used currently can only be used under UV light making it less useful for solar applications. Hereby, we study solid solutions and heterostructures of zinc oxide, aluminum nitride and gallium nitride, which present the possibility to harvest the solar irradiation. These materials can easily be tuned to be better solar photocatalysts. The key parameters necessary for a successful photocatalyst are optimum band gap and band edges of the material, its stability under reaction conditions and the effect of vacancy and interstitials on the material. We ensued a density functional theory (DFT) based investigation to study the effect of different heterojunctions with varying layer thickness towards the band gap and band edge tunability. We found consistent trends of band gap variation with material composition. The effect of anionic vacancies and strain on the materials was also studied. The effect of varying elemental composition at any heterojunction was studied via charge analysis. These materials thus present a versatile platform for material property engineering and present themselves as potential candidates for solar photocatalytic conversion of CO₂.