Powering a CO₂ Reduction Catalyst with Visible Light through Multiple Sub-picosecond Electron Transfers from a Quantum Dot

Abstract

Photosensitization of molecular catalysts to reduce CO to CO is a sustainable route to storable solar fuels. Crucial to the sensitization process is highly efficient transfer of redox equivalents from sensitizer to catalyst; in systems with molecular sensitizers, this transfer is often slow because it is gated by diffusion-limited collisions between sensitizer and catalyst. This article describes the photosensitization of a meso-tetraphenylporphyrin iron(III) chloride (FeTPP) catalyst by colloidal, heavy metal-free CuInS/ZnS quantum dots (QDs) to reduce CO to CO using 450 nm light. The sensitization efficiency (turnover number per absorbed unit of photon energy) of the QD system is a factor of 18 greater than that of an analogous system with a fac-tris(2-phenylpyridine)iridium sensitizer. This high efficiency originates in ultrafast electron transfer between the QD and FeTPP, enabled by formation of QD/FeTPP complexes. Optical spectroscopy reveals that the electron-transfer processes primarily responsible for the first two sensitization steps (FeTPP → FeTPP, and FeTPP → FeTPP) both occur in <200 fs.

Enabling Visible‐Light‐Driven Selective CO2 Reduction by Doping Quantum Dots: Trapping Electrons and Suppressing H2 Evolution

“…In addition to the doping approach, we prepared two reference samples ( Figure 1d): CdS QDs functionalized with Ni 2+ via bridging ligands (CdS-b-Ni), [8] and CdS QDs mixed with Ni 2+ cations in solution, which reach the QD surface through random collisions (CdS-Ni). [19] Theligands in CdS-b-Ni bridge Ni 2+ cations with CdS QDs so that the photoexcited electrons in the QDs can be transferred to the anchored metal cations ( Figures S4-S6).…”

Zinc Thiolate Enables Bright Cu‐Deficient Cu‐In‐S/ZnS Quantum Dots

“…Colloidal quantum dots (QDs) are well suited for low‐cost optoelectronic applications, but are limited in commercial translation because the best‐performing QDs contain cadmium (Cd) and/or lead (Pb). Colloidal copper indium sulfide (CIS) QDs have shown tunable bandgaps, large absorption cross‐sections, and relatively high photoluminescence quantum yields (PLQYs) while approaching the performance of Cd‐ and Pb‐containing QDs for luminescent solar concentrators (LSCs) and photocatalysis . For further successful translation of CIS QDs as an industrially viable colloidal material, attention to the synthetic methods that lead to the rational improvement of optical properties is of interest.…”

Colloidally Stable CdS Quantum Dots in Water with Electrostatically Stabilized Weak‐Binding, Sulfur‐Free Ligands

“…Water is the ultimate green solvent, and the choice of medium for many classes of reactions that utilize an emerging methodology for chemical transformations, nanoparticle photocatalysis, that is highly effective in the laboratory and potentially scalable. [1][2][3] Among the range of nanoparticles that photocatalyze aqueous reactions, semiconductor quantumd ots (QDs) stand out for their chemical and electronic tunability and versatility.Q Ds have demonstrated unprecedented activity in photocatalytic H 2 evolution, [4][5][6][7] unprecedented sensitizatione fficiency for CO 2 reduction, [8] the ability to serve as triplet exciton donors and scaffolds for stereoselective cycloadditions, [9,10] and the electrochemical potentials to act as both photo-oxidant and photo-reductant in CÀCc oupling schemes with no sacrificial reagents. [11,12] In water,p roperly functionalized colloidal QDs form colloidally stable aggregates to mimic the exciton funneling function of photosystemII, [13] and perform chemoselective alcohol oxidations.…”