Perovskite Quantum Dots Encapsulated in a Mesoporous Metal–Organic Framework as Synergistic Photocathode Materials

Abstract

Metal halide perovskite quantum dots, with high light-absorption coefficients and tunable electronic properties, have been widely studied as optoelectronic materials, but their applications in photocatalysis are hindered by their insufficient stability because of the oxidation and agglomeration under light, heat, and atmospheric conditions. To address this challenge, herein, we encapsulated CsPbBr 3 nanocrystals into a stable iron-based metal−organic framework (MOF) with mesoporous cages (∼5.5 and 4.2 nm) via a sequential deposition route to obtain a perovskite-MOF composite material, CsPbBr 3 @PCN-333(Fe), in which CsPbBr 3 nanocrystals were stabilized from aggregation or leaching by the confinement effect of MOF cages. The monodispersed CsPbBr 3 nanocrystals (4−5 nm) within the MOF lattice were directly observed by transmission electron microscopy and corresponding mapping analysis and further confirmed by powder X-ray diffraction, infrared spectroscopy, and N 2 adsorption characterizations. Density functional theory calculations further suggested a significant interfacial charge transfer from CsPbBr 3 quantum dots to , which is ideal for photocatalysis. The CsPbBr 3 @PCN-333(Fe) composite exhibited excellent and stable oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic activities in aprotic systems. Furthermore, CsPbBr 3 @PCN-333(Fe) composite worked as the synergistic photocathode in the photoassisted Li−O 2 battery, where CsPbBr 3 and PCN-333(Fe) acted as optical antennas and ORR/OER catalytic sites, respectively. The CsPbBr 3 @PCN-333(Fe) photocathode showed lower overpotential and better cycling stability compared to CsPbBr 3 nanocrystals or , highlighting the synergy between CsPbBr 3 and PCN-333(Fe) in the composite.

Photoelectrochemistry of oxygen in rechargeable Li–O2 batteries

“…Due to the photon harvest, the reaction pathways towards the OER are altered and strongly rely on the band structures of the semiconductor electrodes. 31,32 In photoelectrocatalytic water splitting, the oxidation potential at the semiconductor electrode is determined by the potential difference between the energy level of the VB and the redox potential of O 2 /H 2 O. 32 This means that, in the photoinvolved Li-O 2 batteries, the semiconductor cathode needs suitable VB energy levels to motivate holes for the photo-excited OER, that is, the VB should be lower than the equilibrium potential of the discharge product.…”

Internal Electric Field and Interfacial Bonding Engineered Step‐Scheme Junction for a Visible‐Light‐Involved Lithium–Oxygen Battery

“…Constructing suitable heterojunction systems, including type-II heterojunctions, p-n junctions, and Schottky junctions, has been applied to inhibit the fast electron-hole recombination and broaden the light absorption range via electronic band association. [25][26][27] The type-II heterojunctions of CsPbBr 3 @PCN-333 and WO 3 /C 3 N 4 have been utilized for Li-O 2 batteries to facilitate the cathode reaction kinetics under the visible-light excitation. The dissociation efficiencies of charge carriers are remarkably improved but at the cost of reduced redox activity from a thermodynamic perspective.…”

Photoelectrochemical energy storage materials: design principles and functional devices towards direct solar to electrochemical energy storage

“…also proposed a novel strategy to encapsulate CsPbBr 3 nanocrystals into a metal−organic framework (MOF) cage to construct a photoactive electrode, which demonstrated an improved stability as a photoassisted Li-O 2 battery. 114…”