(707b) Mie Resonance Induced Photocatalytic CO2 Reduction Using Earth Abundant Dielectric Nanostructures

In this work, we report Mie resonance induced photocatalytic CO₂ reduction and formation of high-value feedstocks using dielectric nanostructures. The reaction of interest is the reverse-water-gas-shift (RWGS) reaction (CO₂ + H_{2 -->} CO + H₂O). This reaction is critical as it addresses multiple objectives, starting with tackling climate change since the conversion of CO₂ to CO is an important approach for the mitigation of anthropogenic CO₂. The further conversion of carbon monoxide (CO) to industrially important methane (CH₄) using the Fischer–Tropsch process. Most of these studies are in their nascent stage in the field of photocatalysis. Currently, plasmonic metal nanostructures (PMNs) such as silver (Ag) and gold (Au) nanoparticles, have been extensively studied to manipulate and amplify light at the nanoscale resulting in a strong electric-field enhancement. This ability resulted from a special property called localized surface plasmon resonance (LSPR). However, there are inherent problems associated with plasmonic metals, such as high heating losses, and poorer compatibility with scaling-up compared to metal-oxide-semiconductor (CMOS) microfabrication processes. Further improvements have been made by hybridizing PMNs with semiconductor metal-oxide. But there are issues with combining two different materials. These limitations prevent the broader use of PMNs in real applications. In this work, we show that the Mie resonance-driven size- and shape-dependent materials that are tunable in the visible to near-infrared regions are an alternative to PMNs. The choice of material in this work is, cuprous oxide (Cu₂O), a p-type semiconductor with a bandgap of 2.1 eV, medium refractive indexed, and dielectric. These nanoparticles offer unique opportunities for reduced dissipative losses and large resonant enhancement of both electric and magnetic near fields on exposure to light. The dielectric materials not only offer high resonant enhancement but also charge carrier generation exhibiting dual properties towards facilitating CO₂ reduction to value feedstocks.