Electrochemical Reduction of CO2 at a TiO2 Electrode using Quantum Dots as Multi-electron Funnels
Abstract
A fundamental difference between colloidal quantum dots (QDs) and organic chromophores is the ability of a QD to mediate multiple charge transfer reactions due to band-edge degeneracy, which allows QDs to accommodate multiple excitons or injected charge carriers, and the availability of multiple sites for charge acceptors to adsorb to QD surfaces. Lead chalocogenide QDs have the highest band-edge degeneracy of the commonly prepared types of QDs. The original goal of this project was to determine the suitability of lead chalcogenide QDs as multi-electron redox centers for shuttling of electrons from a bulk semiconductor to a molecular substrate, in order to catalyze chemical reactions. The PI and her group realized early on in the project that, before they could explore the redox activity of QDs within an electrochemical cell, they needed to determine the fundamental mechanisms of electron exchange between QDs and small molecules, and to optimize the ligand shell of the QDs to provide maximum charge injection/extraction efficiency while maintaining electronic passivation of the QD surface, and thereby preventing chemical corrosion of the QD. While Marcus theory is, in principle, just as applicable to charge transfer processes in QD-molecule systems as it is to molecular systems, the use of Marcus theory to predict the rate of charge separation involving QDs is, in practice, complicated by various heterogeneities and distributions of the chemical and electronic properties of the QD surface. The common theme of the work performed for this project is discovery (and quantitative modeling) of the relationship between the properties of the QD surface and the rate and mechanism charge transfer process. With respect to these goals, the group has made substantial progress using lead sulfide (PbS) QDs with molecular charge-transfer partners in the solution-phase, and has begun to explore the potential for PbS QDs to participate in multi-electron transfer.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 14, 2013
- Accession Number
- AD1013121
Entities
People
- Emily A. Weiss
Organizations
- Northwestern University