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The 90-year-old Hume-Rothery rule was adapted to design an outstanding bifunctional tetra-metallic alloy electrocatalyst for water electrolysis. Following the radius mismatch principles, Fe (131 pm) and Ni (124 pm) are selectively incorporated at the Pd (139 pm) site of Mo 0.30 Pd 0.70 nanosheets. Analogously, Cu (132 pm) alloys with only Pd, while Ag (145 pm) alloys with both Pd and Mo (154 pm). The face-centered cubic Mo 0.30 Pd 0.35 Ni 0.23 Fe 0.12 nanosheets with 10-12 atomic layers, featuring in-plane compressive strain along the {111} basal plane, show 1/3 (422) reflection from local hexagonal symmetry. The more electronegative Pd attracts electron density from Ni/Fe in Mo 0.30 Pd 0.35 Ni 0.23 Fe 0.12 , synergistically boosting the mass activities for hydrogen and oxygen evolution reactions to 89 ± 5 and 38.6 ± 3.1 A g -1 at ±400 mV versus RHE, respectively. Full water electrolysis continues for ≥550 h, requiring cell voltages of 1.51 and 1.63 V at 10 and 100 mA cm -2 , delivering 45 mL h -1 green H 2 .

Advancements in stimuli-driven nanoactuators necessitate the discovery of photo-switchable, self-contained semiconductor nanostructures capable of precise mechanical responses. The reversible assembly of 0D Cs 3 Bi 2 I 9 halide perovskite nanoplatelets (NPLs) between stacked and scattered configurations are demonstrated under light and dark, respectively. This sunlight-triggered perpetual flipping of the NPLs, occurring in less than a minute, is associated with a color change between brown and red. The photomechanical response is driven by the formation and cleavage of sulfide linkages at the NPL surface. In the stacked configuration, various stacking modes create moiré superstructures, enhancing the interlayer charge distribution, and increasing the electronic conductivity and optical absorbance. This leads to a decrease in exciton binding energy from 247 meV for scattered NPLs to 162 meV for stacked NPLs, resulting in a 3.5-fold enhancement in dark current for the stacked NPL films. The switchable control over color and electric current is continuously reversible and retraceable, exhibiting a minor memory effect observed during extended cycling. The self-flipping NPL nanoactuators demonstrate reversible mechanical responses, with topographical oscillations ranging from 14 nm in scattered NPLs to 50 nm in the vertically stacked configuration. This seamless reversible nano-assembly with color interchangeability offers numerous possibilities for nanorobotics, nanoscale switches, and sensors., (© 2024 Wiley‐VCH GmbH.)

Two-dimensional organic-inorganic halide perovskites have emerged as promising candidates for a multitude of optoelectronic technologies, owing to their versatile structure and electronic properties. The optical and electronic properties are harmoniously integrated with both the inorganic metal halide octahedral slab, and the organic spacer layer. The inorganic octahedral layers can also assemble into periodically stacked nanoplatelets, which are interconnected by the organic ammonium cation, resulting in the formation of a superlattice or superstructure. In this perspective, we explore the structural, electronic, and optical properties of lead-free hybrid halides, and the layered halide perovskite single crystals and nanostructures, expanding our understanding of the diverse applications enabled by these versatile structures. The optical properties of the layered halide perovskite single crystals and superlattices are a function of the organic spacer layer thickness, the metal center with either divalent or a combination of monovalent and trivalent cations, and the halide composition. The distinct absorption and emission features are guided by the structural deformation, electron-phonon coupling, and the polaronic effect. Among the diverse optoelectronic possibilities, we have focused on the photodetection capability of layered halide perovskite single crystals, and elucidated the descriptors such as excitonic band gap, effective mass, carrier mobility, Rashba splitting, and the spin texture that decides the direct component of the optical transitions., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The transition from 3D to 2D lead halide perovskites is traditionally led by the lattice incorporation of bulky organic cations. However, the transformation into a coveted 2D superlattice-like structure by cationic substitution at the Pb 2+ site of 3D perovskite is unfamiliar. It is demonstrated that the gradual increment of [Sn 2+ ] alters the FASn x Pb 1- x I 3 nanocrystals into the Ruddlesden-Popper-like nanoplatelets (NPLs), with surface-absorbed oleic acid (OA) and oleylamine (OAm) spacer ligand at 80 °C (FA + : formamidinium cation). These NPLs are stacked either by a perfect alignment to form the superlattice or by offsetting the NPL edges because of their lateral displacements. The phase transition occurs from the Sn/Pb ratio ≥0.011, with 0.64 wt% of Sn 2+ species. At and above Sn/Pb = 0.022, the NPL superlattice stacks start to grow along [00l] with a repeating length of 4.37(3) nm, comprising the organic bilayer and the inorganic block having two octahedral layers (n = 2). Besides, a photoluminescence quantum yield of 98.4% is obtained with Sn/Pb = 0.011 (n ≥ 4), after surface passivation by trioctylphosphine (TOP)., (© 2023 Wiley-VCH GmbH.)

Phase pure, trigonal, mesoporous Fe/Al/La trimetallic nano-oxide (abbreviated as FAL) was synthesized using energy efficient chemical route with bandgap 1.97 eV and S BET  = 50.02 m 2 /g and an average pore size of 8.95 nm for photodegradation of azo (di and tri) and thiazine class of dyes successfully. The valence band and conduction band potentials were calculated using the Mott-Schottky plot. The highest photodegradation efficiency was 93.85 ± 2% for reactive black 5 (RB5) at pH 7 under solar irradiation. The phase formation of FAL was confirmed by PXRD, TEM, and HRTEM analyses. The other characterizations include FESEM, Raman, EPR, UV, HPLC, LC-MS, etc. The presence of the metal centers and their corresponding oxidation states were confirmed by the SAEDS, elemental mapping, and XPS analyses respectively. FAL was also able to photodegrade direct blue 71 (DB71) and methylene blue (MB) under the same condition at different pH efficiently (pH 2-11). The photodegradation obeyed the pseudo-1st-order kinetics and was reusable up to 5 successive cycles. This study may be an efficient tool to meet UNs' SDG:6., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The increasingly popular, lead-free perovskite, Cs 3 Bi 2 I 9 has a vulnerable Bi 3+ state under reductive potentials, due to the high standard reduction potential of Bi 3+ /Bi δ + (0 < δ < 3). Contrary to this fundamental understanding, herein, ligand-coated Cs 3 Bi 2 I 9 nanodiscs (NDs) demonstrate outstanding electrochemical stability with up to -1 V versus a saturated calomel electrode in aqueous 0.63 M (5% v/v) and 6.34 M (50% v/v) hydroiodic acid (HI), with a minor BiI 3 fraction due to the unavoidable partial aqueous disintegration of the perovskite phase after 8 and 16 h, respectively. A dynamic equilibrium of saturated 0.005 M NDs maintains the common ion effect of I - , and remarkably stabilizes ∼93% Bi 3+ in 0.63 M HI under a strong reductive potential. In comparison, the hexagonal phase of bulk Cs 3 Bi 2 I 9 disintegrates considerably in the semi-aqueous media. Lowering the concentration of synthetic HI from the commonly used ∼50% v/v by elevating the pH from -0.8 to 0.2 helps in reducing the cost per unit of H 2 production. Our Cs 3 Bi 2 I 9 NDs with a hexagonal lattice have 4-6 (002) planes stacked along the c -axis. With 0.005 M photostable NDs, 22.5 μmol h -1 H 2 is photochemically obtained within 8 h in a 6.34 M HI solution. Electrocatalytic H 2 evolution occurs with a turnover frequency of 11.7 H 2 per s at -533 mV and outstanding operational stability for more than 20 h.

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 Ni 2+ and Co 2+ with similar ionic radii of ∼0.07 nm in the interlayer of 1T-WS 2 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-WS 2 , 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-WS 2 . 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/cm 2 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-WS 2 and the number of active sites. While 1T-WS 2 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.

In this study, a comprehensive investigation is carried out to examine the sensitivity of tropospheric relative humidity (RH) on monsoon depressions (MDs) under a changing climate regime through surrogate climate change approach over the Indian region. Composite analysis of four MDs show a persistent warming (RH2+) and cooling (RH2-) throughout the troposphere in the sensitivity experiments. In-depth analysis of a MD over the Arabian Sea (AS) exhibits sustained warming for RH2+, which is accredited to 2.6% increase in stratiform clouds accounting for 13% increment in heating, whereas 5% increment in convective clouds hardly contribute to total heating. Frozen hydrometeors (graupel and snow) are speculated to be the major contributors to this heating. Stratiform clouds showed greater sensitivity to RH perturbations in the lower troposphere (1000-750 hPa), albeit very less sensitivity for convective clouds, both in the lower and mid-troposphere (700-500 hPa). Precipitation is enhanced in a moist situation (RH2+) owing to positive feedbacks induced by moisture influx and precipitation efficiency, while negative feedbacks suppressed precipitation in a dry troposphere (RH2-). In a nutshell, it is inferred that under moist (dry) situations, it is highly likely that intense (weak) MDs will occur in the near future over the Indian region.