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Moritz Kuehnel1 2 David Wakerley2 Katherine Orchard2 Kristian Dalle2 Constantin Sahm2 Gaia Neri3 Jonathan Lee3 Alexander Cowan3 Erwin Reisner2

1, Swansea University, Swansea, , United Kingdom
2, University of Cambridge, Cambridge, , United Kingdom
3, University of Liverpool, Liverpool, , United Kingdom

Direct photochemical conversion of H2O and CO2 into H2 and CO is a promising strategy to mitigate CO2 emissions and simultaneously store solar energy in renewable fuels, but most of the currently known catalysts for this purpose are based on precious metals, require organic solvents or suffer from low stability and selectivity.

We study hybrid materials that combine the photophysical properties of semiconductor nanocrystals with the selectivity of well-defined molecular electrocatalysts. Engineering the particle surface is of paramount importance to achieve efficient charge transfer in such a system. By designing material-specific surface anchors, we can attach molecular catalysts to chalcogenide quantum dots (QDs) to drive H2 evolution and CO2 reduction with visible light in water. Direct comparison of different anchoring groups allows us to correlate the photocatalytic activity with the QD/catalyst interface.[1] We use transient absorption spectroscopy to follow the charge-transfer processes in hybrid photocatalysts.

We further develop novel strategies to control the competition between CO2 reduction and H2 evolution from aqueous QDs, by exploiting the often overlooked effects of capping ligands on their photocatalytic activity.[2] Modulating the capping ligand surface coverage not only allows us to control the H2/CO selectivity, but it also reveals new reactivities such as tuneable formic acid decomposition and biomass photoreforming.[3-4]

References
[1] J. Amer. Chem. Soc., 2017, 139, 7217; [2] J. Mat. Chem. A, 2016, 4, 2856; [3] Angew. Chem. Int. Ed., 2015, 54, 9627; [4] Nat. Energy, 2017, 2, 201721.

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