Embedded growth of colorful CsPbX3 (X = Cl, Br, I) nanocrystals in metal−organic frameworks at Room Temperature

Herein, we develop a novel strategy for preparing all-inorganic cesium lead halide (CsPbX3, X= Cl, Br, I) perovskite nanocrystals (NCs)@Zn-based metal-organic framework (MOF) composites through interfacial synthesis. The successful embedding of fluorescent perovskite NCs in Zn-MOFs is due to the in-situ confined growth, which is attributed to the re-nucleation of water-triggered phase transformation from Cs4PbBr6 to CsPbBr3. The controllable synthesis of mixed-halide based composites with various emission wavelength can be achieved by adding the desired amount of halide (Cl or I) salts in the re-nucleation process. More importantly, the anion exchange reaction is inhibited among various composites with different halogen atoms by being trapped in MOFs. Besides, a white light-emitting diode (WLED) is produced using a blue LED chip with the green-emitting and red-emitting composites, which has a color coordinate of (0.3291, 0.3272) and a wide color gamut. This work provides a novel route to achieving perovskite NCs growth in MOFs, which also can be extended to the other NCs embedded in frames as well.

NiCo2S4 nanosheets decorated on nitrogen-doped hollow carbon nanospheres as advanced electrodes for high-performance asymmetric supercapacitors

Taking advantage of both Faradaic and carbonaceous materials is an efficient way to synthesize composite electrodes with enhanced performance for supercapacitors. In this study, NiCo2S4 nanoflakes were grown on the surface of nitrogen-doped hollow carbon nanospheres (NHCSs), forming a NiCo2S4/NHCS composite with a core-shell structure. This three-dimensionally confined growth of NiCo2S4 can effectively inhibit its aggregation and facilitate mass transport and charge transfer. Accordingly, the NiCo2S4/NHCS composite exhibited high cycling stability with only 9.2% capacitance fading after 10,000 cycles, outstanding specific capacitance of 902 F g−1 at 1 A g−1, and it retained 90.6% of the capacitance at 20 A g−1. Moreover, an asymmetric supercapacitor composed of NiCo2S4/NHCS and activated carbon electrodes delivered remarkable energy density (31.25 Wh kg−1 at 750 W kg−1), excellent power density (15003 W kg−1 at 21.88 Wh kg−1), and satisfactory cycling stability (13.4% capacitance fading after 5000 cycles). The outstanding overall performance is attributed to the synergistic effect of the NiCo2S4 shell and NHSC core, which endows the composite with a stable structure, high electrical conductivity, abundant active reaction sites, and short ion-transport pathways. The synthesized NiCo2S4/NHCS composite is a competitive candidate for the electrodes of high-performance supercapacitors.