| Autor: |
Hernandez F; Department of Chemistry, Amherst College, Amherst, MA 01002, USA. jolshansky@amherst.edu., Yang M; Department of Chemistry, Amherst College, Amherst, MA 01002, USA. jolshansky@amherst.edu., Nagelj N; Department of Chemistry, Amherst College, Amherst, MA 01002, USA. jolshansky@amherst.edu., Lee AY; Department of Chemistry, Amherst College, Amherst, MA 01002, USA. jolshansky@amherst.edu., Noh H; Department of Chemistry, Amherst College, Amherst, MA 01002, USA. jolshansky@amherst.edu., Hur KP; Department of Chemistry, Amherst College, Amherst, MA 01002, USA. jolshansky@amherst.edu., Fu X; Department of Chemistry, Amherst College, Amherst, MA 01002, USA. jolshansky@amherst.edu., Savoie CJ; Department of Chemistry, Amherst College, Amherst, MA 01002, USA. jolshansky@amherst.edu., Schwartzberg AM; The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA., Olshansky JH; Department of Chemistry, Amherst College, Amherst, MA 01002, USA. jolshansky@amherst.edu. |
| Abstrakt: |
Photocatalytic CO 2 reduction offers a promising strategy to produce hydrocarbons without reliance on fossil fuels. Visible light-absorbing colloidal nanomaterials composed of earth-abundant metals suspended in aqueous media are particularly attractive owing to their low-cost, ease of separation, and highly modifiable surfaces. The current study explores such a system by employing water-soluble ZnSe quantum dots and a Co-based molecular catalyst. Water solubilization of the quantum dots is achieved with either carboxylate (3-mercaptopropionic acid) or ammonium (2-aminoethanethiol) functionalized ligands to produce nanoparticles with either negatively or positively-charged surfaces. Photocatalysis experiments are performed to compare the effectiveness of these two surface functionalization strategies on CO 2 reduction and ultrafast spectroscopy is used to reveal the underlying photoexcited charge dynamics. We find that the positively-charged quantum dots can support sub-picosecond electron transfer to the carboxylate-based molecular catalyst and also produce >30% selectivity for CO and >170 mmol CO g ZnSe -1 . However, aggregation reduces activity in approximately one day. In contrast, the negatively-charged quantum dots exhibit >10 ps electron transfer and substantially lower CO selectivity, but they are colloidally stable for days. These results highlight the importance of the quantum dot-catalyst interaction for CO 2 reduction. Furthermore, multi-dentate catalyst molecules create a trade-off between photocatalytic efficiency from strong interactions and deleterious aggregation of quantum dot-catalyst assemblies. |
