Near Unity Quantum Yield of Light-Driven Redox Mediator Reduction and Efficient H₂ Generation Using Colloidal Nanorod Heterostructures

Abstract

The advancement of direct solar-to-fuel conversion technologies requires the development of efficient catalysts as well as efficient materials and novel approaches for light harvesting and charge separation. We report a novel system for unprecedentedly efficient (with near-unity quantum yield) light-driven reduction of methylviologen (MV2+), a common redox mediator, using colloidal quasi-type II CdSe/CdS dot-in-rod nanorods as a light absorber and charge separator and mercaptopropionic acid as a sacrificial electron donor. In the presence of Pt nanoparticles, this system can efficiently convert sunlight into H2, providing a versatile redox mediator-based approach for solar-to-fuel conversion. Compared to related CdSe seed and CdSe/CdS core/shell quantum dots and CdS nanorods, the quantum yields are significantly higher in the CdSe/CdS dot-in-rod structures. Comparison of charge separation, recombination and hole filling rates in these complexes showed that the dot-in-rod structure enables ultrafast electron transfer to methylviologen, fast hole removal by sacrificial electron donor and slow charge recombination, leading to the high quantum yield for MV2+ photoreduction. Our finding demonstrates that by controlling the composition, size and shape of quantum-confined nanoheterostructures, the electron and hole wave functions can be tailored to produce efficient light harvesting and charge separation materials.

Photogeneration of hydrogen from water using CdSe nanocrystals demonstrating the importance of surface exchange

“…In this way, NCs can offer unique size-dependent optical properties and stronger light absorption over a wider spectral range than do molecular PSs (68,76). In fact, NCs as light absorbers in combination with precious metal proton reduction catalysts or with Fe-Fe hydrogenase have been studied, yielding interesting photocatalytic systems (77)(78)(79)(80)(81).…”

Auger-Assisted Electron Transfer from Photoexcited Semiconductor Quantum Dots

“…[1][2][3][4][5][6][7][8] For these applications, one of the most fundamental and crucial steps is the dissociation of excitons (bound electron-hole pairs) in these materials through interfacial charge (electron or hole) transfer to acceptor materials. Due to the strong electron-nuclear interaction in molecules, inter-and intra-molecular electron transfer (ET) is accompanied by large rearrangement of the nuclear configuration, which are described by the Marcus ET theory, [9][10][11][12] exhibiting the well-known dependences of ET rates on the driving force in the Marcus normal, barrier-less, and inverted regimes.…”

Quantum Dots for Visible-Light Photocatalytic CO2 Reduction

“…This leads to greater charge separation and transfer efficiency and slow charge recombination, which result in near-unity quantum yield of MV 2þ photoreduction ( Figure 12). 33 This effort can also substantially benefit from advances in theoretical modeling, which still lags in this field. The better integration of experimental research and computational investigation can help understand the structureefunction relationship, guide the rational synthesis of materials with predictable properties, and accelerate the discovery of new materials with optimized function (Figure 13).…”

“…129e131 A variety of hole scavengers and capping molecules can potentially be used to improve the stability of the CdSe-sensitized TiO 2 photocatalysts. 33,34 To further extend the photocatalytic activity of TiO 2 for CO 2 reduction to longer wavelengths, small band-gap PbS QDs are successfully used as sensitizers. 28 The PbS QDs are attached to the surface of Cu/TiO 2 photocatalysts by the linker molecule 3-mercaptopropionic acid.…”