The role of electrochemical interfaces in energy conversion and storage is unprecedented and more so the interlayers of two-dimensional (2D) heterostructures, where the physicochemical nature of these interlayers can be adjusted by cation intercalation. We demonstrate in situ intercalation of Ni2+ and Co2+ with similar ionic radii of ∼0.07 nm in the interlayer of 1T-WS2 while electrodepositing NiCo layered double hydroxide (NiCo-LDH) to create a 2D heterostructure. The extent of intercalation varies with the electrodeposition time. Electrodeposition for 90 s results in 22.4-nm-thick heterostructures, and charge transfer ensues from NiCo-LDH to 1T-WS2, which stabilizes the higher oxidation states of Ni and Co. Density functional theory calculations validate the intercalation principle where the intercalated Ni and Co d electrons contribute to the density of states at the Fermi level of 1T-WS2. Water electrolysis is taken as a representative redox process. The 90 s electrodeposited heterostructure needs the relatively lowest overpotentials of 134 ± 14 and 343 ± 4 mV for hydrogen and oxygen evolution reactions, respectively, to achieve a current density of ±10 mA/cm2 along with exceptional durability for 60 h in 1 M potassium hydroxide. The electrochemical parameters are found to correlate with enhanced mass diffusion through the cation and Cl–-intercalated interlayer spacing of 1T-WS2 and the number of active sites. While 1T-WS2 is mostly celebrated as a HER catalyst in an acidic medium, with the help of intercalation chemistry, this work explores an unfound territory of this transition-metal dichalcogenide to catalyze both half-reactions of water electrolysis.

The increasingly popular, lead-free perovskite, Cs3Bi2I9 has a vulnerable Bi3+ state under reductive potentials, due to the high standard reduction potential of Bi3+/Bi+ (0 < δ < 3). Contrary to...

Metal halide perovskite (MHP) nanocrystals (NCs) having different dimensionalities are considered as stable alternatives to the 3D bulk perovskites as photo absorbers in photovoltaic and optoelectronic devices. The MHP NCs with confinement effects along one or more directions can be synthesized in a relatively more pure form than the bulk perovskites as a result of the coordination of surface ligands with the perovskite phase. Moreover, the MHP NC growth and crystallization, morphology changes, and crystallographic facet engineering largely depend on the reaction conditions, the choice of ligands, as well as the precursor type and concentration. Despite having very rich electronic and optical properties both in the solution and in the films, the MHP NC films are limited by the impediments of NC-connectivity and carrier trapping. Herein, appropriate passivation methods and antisolvent treatment are needed to render good quality films with bright luminescence. This perspective highlights the advantages and challenges of the MHP nanostructures for photovoltaics and optoelectronics due to their nucleation and growth processes, film preparation, surface chemistry, dimensionality, and electronic and optical properties.

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