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Essays on Mie resonance: Fundamental study to uphill catalysis

Ramakrishnan, Sundaram Bhardwaj
The Global CO₂ concentrations have reached levels of ~ 415 ppm in the atmosphere and have been linked to climate change and ocean acidification. In addition to having a detrimental effect on the planet, it also causes humans adverse health risks. The major source of CO₂ emissions in the U.S. is largely driven by transportation (35%) and industry (30%). Within the industry, decarbonization can be traced to the top five of the largest emitters of CO₂: petroleum refining, chemicals, iron and steel, cement, and food and beverage. All these processes are energy intensive in nature. Hence, all the energy required by these industries has been supplied by conventional coal/gasoline energy sources. To achieve a clean and equitable energy economy and address the climate crisis, we need to accelerate the large-scale development and deployment of renewable energy technology to support an equitable transition to a decarbonized energy system. In this work, we aim to develop earth-abundant, inexpensive copper-based nanomaterials as solar-thermal-driven photocatalysts. The field of nano-photocatalysis is dominated by plasmonic metal nanostructures (PMNs) namely gold (Au) and silver (Ag). These plasmonic materials exhibit Mie resonance when they interact with light. The most used plasmonic materials are gold (Au), silver (Ag), Aluminum (Al), and Cu. These plasmonic materials, due to their strong light adsorption in the visible region can harvest large fractions of the solar light. The strong light absorbing property is a result of a special property called localized surface plasmon resonance (LSPR) which is caused by coherent collective oscillation of free electrons (conduction band) known as “plasmons”. The frequency of the LSPR depends on the shape and size of the nanoparticle. On the other hand, Mie resonances are also exhibited in dielectric materials, which are medium-refractive-indexed and metal-oxide. These dielectric Mie resonances are also tunable by geometry. The material of interest in this work is Copper (Cu), Cuprous oxide (Cu₂O), and Cupric oxide (CuO). We can perform catalysis directly, on the surface of Cu/Cu₂O/CuO, or hybridize them with other catalytic materials like palladium (Pd). The materials will be tested for Reverse-Water-Gas-Shift-Reaction (RWGSR) and C-C coupling as a probe reaction to assess their performance.