Tuning the local chemical environment of ZnSe quantum dots with dithiols towards photocatalytic CO<sub>2</sub> reduction

Sahm, Constantin D, Ciotti, Anna, Mates-Torres, Eric, Badiani, Vivek, Sokolowski, Kamil, Neri, Gaia, Cowan, Alexander J ORCID: 0000-0001-9032-3548, Garcia-Melchor, Max and Reisner, Erwin
(2022) Tuning the local chemical environment of ZnSe quantum dots with dithiols towards photocatalytic CO<sub>2</sub> reduction. CHEMICAL SCIENCE, 13 (20). pp. 5988-5998.

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Sunlight-driven CO<sub>2</sub> reduction to renewable fuels is a promising strategy towards a closed carbon cycle in a circular economy. For that purpose, colloidal quantum dots (QDs) have emerged as a versatile light absorber platform that offers many possibilities for surface modification strategies. Considerable attention has been focused on tailoring the local chemical environment of the catalytic site for CO<sub>2</sub> reduction with chemical functionalities ranging from amino acids to amines, imidazolium, pyridines, and others. Here we show that dithiols, a class of organic compounds previously unexplored in the context of CO<sub>2</sub> reduction, can enhance photocatalytic CO<sub>2</sub> reduction on ZnSe QDs. A short dithiol (1,2-ethanedithiol) activates the QD surface for CO<sub>2</sub> reduction accompanied by a suppression of the competing H<sub>2</sub> evolution reaction. In contrast, in the presence of an immobilized Ni(cyclam) co-catalyst, a longer dithiol (1,6-hexanedithiol) accelerates CO<sub>2</sub> reduction. <sup>1</sup>H-NMR spectroscopy studies of the dithiol-QD surface interactions reveal a strong affinity of the dithiols for the QD surface accompanied by a solvation sphere governed by hydrophobic interactions. Control experiments with a series of dithiol analogues (monothiol, mercaptoalcohol) render the hydrophobic chemical environment unlikely as the sole contribution of the enhancement of CO<sub>2</sub> reduction. Density functional theory (DFT) calculations provide a framework to rationalize the observed dithiol length dependent activity through the analysis of the non-covalent interactions between the dangling thiol moiety and the CO<sub>2</sub> reduction intermediates at the catalytic site. This work therefore introduces dithiol capping ligands as a straightforward means to enhance CO<sub>2</sub> reduction catalysis on both bare and co-catalyst modified QDs by engineering the particle's chemical environment.

Item Type: Article
Divisions: Faculty of Science and Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 12 Apr 2022 13:25
Last Modified: 19 Oct 2023 09:33
DOI: 10.1039/d2sc00890d
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3152779