SusChEM: Visible Light-Driven Reduction of Carbon Dioxide using Heavy Metal-Free Colloidal Quantum Dots as Sensitizers

Many reactions that produce, or facilitate the production of, fuels – including the reduction of CO2 to methanol or methane or to CO as an input for the H2-forming water-gas shift reaction – require multiple reductions or oxidations, or both, of small-molecule substrates. These “redox” reactions can be conducted even more sustainably by powering them with sunlight, through the use of a photo-redox catalyst. An ideal photo-redox catalyst for fuel production through proton-coupled reduction of CO2 addresses both the thermodynamic and kinetic challenges of these reactions: it uses visible or lower-energy light to produce reducing equivalents with adequate potentials to form the final products AND has means of lowering kinetic barriers for proton-coupled electron transfer reactions. The objective of the proposed work is to identify and optimize the most important thermodynamic and kinetic parameters in the performance of ternary heavy metal-free colloidal CuInX2 (X = S, Se) quantum dots (QDs) as soluble, multi-site, colloidal sensitizers for photocatalysis of the reduction of CO2 in solution. In the systems under study, the QD serves as a visible-light photosensitizer for a series of known molecular CO2 reduction catalysts.