Pyridinethiolate-Capped CdSe Quantum Dots for Red-Light-Driven H2 Production in Water.

The utilization of low-energy sunlight to produce renewable fuels is a subject of great interest. Here we report the first example of metal chalcogenide quantum dots (QDs) capped with a pyridinethiolate carboxylic acid (pyS-COOH) for red-light-driven H2 production in water. The precious-metal-free system is robust over 240 h, and achieves a turnover number (TON) of 43910 ± 305 (vs Ni) with a rate of 31570 ± 1690 mmol g-1 h-1 for hydrogen production. In contrast to the inactive QDs capped with other thiolate ligands, the CdSe-pyS-COOH QDs give a significantly higher singlet oxygen quantum yield [ΦΔ (1O2)] in solution.

Photocatalytic CO2 reduction with aminoanthraquinone organic dyes.

The direct utilization of solar energy to convert CO2 into renewable chemicals remains a challenge. One essential difficulty is the development of efficient and inexpensive light-absorbers. Here we show a series of aminoanthraquinone organic dyes to promote the efficiency for visible light-driven CO2 reduction to CO when coupled with an Fe porphyrin catalyst. Importantly, high turnover numbers can be obtained for both the photosensitizer and the catalyst, which has not been achieved in current light-driven systems. Structure-function study performed with substituents having distinct electronic effects reveals that the built-in donor-acceptor property of the photosensitizer significantly promotes the photocatalytic activity. We anticipate this study gives insight into the continued development of advanced photocatalysts for solar energy conversion.

Efficient Red-Light-Driven Hydrogen Evolution with an Anthraquinone Organic Dye.

The direct utilization of the full solar spectrum to obtain renewable fuels remains a challenge because the conversion of the low-energy light (red and near-infrared) is difficult. Current light-driven systems show activity for hydrogen generation with the high-energy part of sunlight. Here we report the use of a simple anthraquinone organic dye in an artificial photosynthetic system that promotes efficient red-light-driven production of hydrogen. The system contains no noble metal and exhibits a turnover number greater than 0.78 million and a quantum yield of 30.6% at 630 nm. A mechanistic study revealed that the excited-state and redox properties of the chromophore are critical to achieving high activity and stability.

Selective CO2 Reduction to Ethylene Using Imidazolium-Functionalized Copper.

Electrochemical CO2 reduction is a promising approach to obtain sustainable chemicals in energy conversion. Improving the selectivity of CO2 reduction toward a particular C2 product such as ethylene remains a significant challenge. Herein, we report a series of imidazolium hexafluorophosphate compounds as surface modifiers for planar Cu foils to boost the Faradaic efficiency (FE) of ethylene from 5 to 73%, which is among the highest reported using polycrystalline Cu. The modified electrodes are convenient to prepare. The structure-function study demonstrates that varying the alkyl or aromatic substituents on the imidazolium nitrogen atoms has significant effects on the morphology of the deposited films and the product selectivity of CO2 reduction. Experimental FEC≥2, FEC2H4, ln(FEC≥2/FECH4), and ln(FEC2H4/FEC2H5OH) values show generally linear relationships with FEH2 while using different imidazolium modifiers, suggesting that factors governing proton reduction may also be directly related to both overall C≥2 generation and ethylene selectivity. This work presents an effective and practical way in tailoring the active sites of metallic surface for selective CO2 reduction.

Promoting photocatalytic CO2 reduction with a molecular copper purpurin chromophore.

CO2 reduction through artificial photosynthesis represents a prominent strategy toward the conversion of solar energy into fuels or useful chemical feedstocks. In such configuration, designing highly efficient chromophores comprising earth-abundant elements is essential for both light harvesting and electron transfer. Herein, we report that a copper purpurin complex bearing an additional redox-active center in natural organic chromophores is capable to shift the reduction potential 540 mV more negative than its organic dye component. When this copper photosensitizer is employed with an iron porphyrin as the catalyst and 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole as the sacrificial reductant, the system achieves over 16100 turnover number of CO from CO2 with a 95% selectivity (CO vs H2) under visible-light irradiation, which is among the highest reported for a homogeneous noble metal-free system. This work may open up an effective approach for the rational design of highly efficient chromophores in artificial photosynthesis.