Metal halide perovskites have attracted substantial interest because of their promising properties for optoelectronic applications. Despite much progress made in the field, the exact growth mechanism of perovskite nanocrystals (e.g., CsPbBr 3 ) remains elusive and further improvement of their controllable synthesis is challenging. Herein, we point out different phenomena during the processes of growth, cooling, and purification of high-quality CsPbBr 3 nanocrystals using in situ photoluminescence spectroscopy. The as-synthesized materials have been further characterized by timeresolved transient differential transmission and photoluminescence spectroscopies. Using X-ray scattering, we confirm that nanocrystals form superstructures during the process of cooling already in dispersion, which is frequently ignored. The purification process is explained using a proposed model based on the self-size-selection. On the one hand, such superstructures pave a potential pathway to the fabrication of highquality devices such as light-emitting devices. On the other hand, the approach to reveal their formation process benefits the comparison and understanding of the difference between nanocrystals and supercrystals. The fact that superstructures form already during synthesis may also apply to the different perovskite systems and thus help to improve the quality of the as-prepared nanocrystals.
It usually requires high temperature and high pressure to reform methanol with water to hydrogen with high turnover frequency (TOF). Here we show that hydrogen can be produced from alkaline methanol on al ight-triggered multilayer system with avery high hydrogen evolution rate up to ca. 1 mmol s À1 under the illumination of as tandardP t-decorated carbon nitride.T he system can achieve ar emarkable TOFu p to 1.8 10 6 moles of hydrogen per mole of Pt per hour under mild conditions.T he total turnover number (TTN) of 470 000 measured over 38 hours is among the highest reported. The system does not lead to any CO x emissions,hence it could feed clean hydrogen to fuel cells.Incontrast to aslurry system, the proposed multi-layer system avoids particle aggregation and effectively uses light and Pt active sites.The performance is also attributed to the light-triggered reforming of alkaline methanol. This notable performance is apromising step toward practical light-driven hydrogen generation.
Artificial photosynthesis of alcohols from CO2 is still unsatisfactory owing to the rapid charge relaxation compared to the sluggish photoreactions and the oxidation of alcohol products. Here, we demonstrate that CO2 is reduced to methanol with 100 % selectivity using water as the only electron donor on a carbon nitride‐like polymer (FAT) decorated with carbon dots. The quantum efficiency of 5.9 % (λ=420 nm) is 300 % higher than the previously reported carbon nitride junction. Using transient absorption spectroscopy, we observed that holes in FAT could be extracted by the carbon dots with nearly 75 % efficiency before they become unreactive by trapping. Extraction of holes resulted in a greater density of photoelectrons, indicative of reduced recombination of shorter‐lived reactive electrons. This work offers a strategy to promote photocatalysis by increasing the amount of reactive photogenerated charges via structure engineering and extraction before energy losses by deep trapping.
Metal halide perovskites are promising materials for a range of applications. The synthesis of light-emitting perovskite nanorods has become popular recently. Thus far, the facile synthesis of perovskite nanorods remains elusive. In this work, we have developed a facile synthesis to fabricate FAPbI 3 nanorods for the first time, demonstrating a high photoluminescence quantum yield of 35-42%. The fabrication of the nanorods has been made possible by carefully tuning the concentration of formamidine-oleate as well as the amount of oleic acid with pre-dissolved PbI 2 in toluene with oleic acid/oleylamine.
Hydrogen production from methanol has attracted substantial interest because of the clean combustion of hydrogen and the convenience of methanol in storage and transportation. However, it requires high-temperature and high-pressure conditions to reform methanol with water to hydrogen with high turnover frequency (TOF, e.g. 104 moles of hydrogen per mole of Pt per hour). Here we show that hydrogen can be produced from anhydrous alkaline methanol with a remarkable TOF of 1.8×106 moles of hydrogen per mole of Pt per hour on a light-triggered multi-layer system under mild conditions. The performance is attributed to the use of anhydrous methanol as both the proton source and the hole scavenger in alkaline conditions. In contrast to a slurry system, we show that the proposed multi-layer system avoids particle aggregation, and it leads to the effective utilization of methanol, light and Pt active sites. This notable performance steps forward to the practical light-triggered hydrogen generation.
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