PtCoFe nanowires with different alloying compositions are chemically prepared and acted as counter electrodes (CEs) in dye‐sensitized solar cells (DSSCs) with Ru(II)‐based dyes. Due to their superior ...I3− reduction activity, PtCoFe nanowires with rich (111) facets enhance the performance of DSSCs. Hence, N719 DSSCs with PtCoFe nanowires, respectively, produce better power conversion efficiency (PCE) of 8.10% for Pt33Co24Fe43 nanowire, 8.33% for Pt74Co12Fe14 nanowire, and 9.26% for Pt49Co23Fe28 nanowire in comparison to the PCE of Pt CE (7.32%). Further, the PRT‐22 DSSC with Pt49Co23Fe28 nanowire exhibits a maximum PCE of 12.29% with a certificated value of 12.0%, which surpass the previous PCE record of the DSSCs with Ru(II)‐based dyes. The photovoltaic and electrochemical results reveal the composition‐dependent activity along with a volcano‐shaped trend in the I−/I3− redox reaction. Theoretical work on the adsorption energies of I2, the desorption energies of I−, and the corresponding absolute energy demonstrates that the I3− reduction activity followed in the order of Pt49Co23Fe28(111) plane > Pt74Co12Fe14(111) plane > Pt33Co24Fe43(111) plane, proving Pt49Co23Fe28 nanowire to be a superior cathode material for DSSCs.
PtCoFe nanowires with rich (111) planes are chemically prepared and act as the counter electrodes of dye‐sensitized solar cells (DSSCs). Evidently, Pt49Co23Fe28 nanowires demonstrate the superior catalytic properties with respect to the I−/I3− redox reactions. Thus, PRT‐22 DSSC based on Pt49Co23Fe28 nanowire produces an impressive power conversion efficiency of 12.29%.
Antiaromatic compounds have recently received considerable attention because of their novel properties such as narrow HOMO–LUMO gaps and facile formation of mutual stacking. Here, the spontaneous ...assembly of antiaromatic meso‐2‐thienyl‐substituted 5,15‐dioxaporphyrin (DOP‐1) is scrutinized at the liquid‐solid interface by scanning tunneling microscopy (STM). Polymorphism in monolayers characterized by the orthogonal and parallel assemblies is found at the low concentration of 0.05 mM. The parallel assembly is more stable and dominantly formed at higher concentrations. Aggregation was observed at concentrations >0.2 mM, and the STM images of the aggregates implied the formation of stacked layers. The intrinsic electronic structures of the mutually stacked bilayer generated by applying an electric pulse to the monolayer were probed by scanning tunneling spectroscopy to reveal the narrowing of the HOMO–LUMO gap by about 20 % compared with the monolayer, thus suggesting significant molecular orbital interactions.
The spontaneous assembly of antiaromatic meso‐2‐thienyl‐substituted 5,15‐dioxaporphyrin (DOP‐1) has been studied at the liquid‐solid interface to elucidate its polymorphism in a monolayer and the facile formation of the stacked layer. The study of the intrinsic electronic structures of the stacked bilayer by scanning tunneling spectroscopy revealed a narrowing of the HOMO–LUMO gap compared to the monolayer, thus suggesting significant molecular orbital interactions.
Constructing two-dimensional (2D), free-standing, nonprecious, and robust electrocatalysts for oxygen evolution reactions (OERs) is of primary importance in the commercial water-splitting technology. ...Herein, we have constructed a 2D heterostructured NiFe2O4/NiFe layered double hydroxides (LDH) mixed composite on a low-cost stainless-steel mesh substrate using a low-temperature one-step wet chemical synthesis method and have also investigated the effect of starting material concentration on the formation of the NiFe2O4/NiFe LDH mixed composite. The as-prepared NiFe2O4/NiFe LDH-25 electrocatalyst drives a 100 mA/cm2 OER with the lowest reported overpotential of 190 mV and a Tafel slope 21.5 mV/dec and drives a stable 100 mA/cm2 OER process in 1 M KOH. These OER activities are superior to that of the state-of-the-art RuO2 OER electrocatalyst. The excellent OER activity appears to be due to the synergetic effect of NiFe LDHs and NiFe2O4. In addition, the vertically aligned heterostructure of the NiFe2O4/NiFe LDH composite thin sheets provides a large number of active edge sites, directly attached to the highly conducting substrate, which contributes to improving the electronic conductivity of the electrocatalyst. This work provides valuable insight into the design and one-step synthesis of NiFe2O4/NiFe LDH bimetallic mixed oxide and hydroxide composite thin films with enhanced OER activity and stability as well as deciphering the origin of the OER enhancement by metal oxides and metal hydroxides.
The compound 6‐azaindole undergoes self‐assembly by formation of N(1)−H⋅⋅⋅N(6) hydrogen bonds (H bonds), forming a cyclic, triply H‐bonded trimer. The formation phenomenon is visualized by scanning ...tunneling microscopy. Remarkably, the H‐bonded trimer undergoes excited‐state triple proton transfer (ESTPT), resulting in a proton‐transfer tautomer emission maximized at 435 nm (325 nm of the normal emission) in cyclohexane. Computational approaches affirm the thermodynamically favorable H‐bonded trimer formation and the associated ESTPT reaction. Thus, nearly half a century after Michael Kasha discovered the double H‐bonded dimer of 7‐azaindole and its associated excited‐state double‐proton‐transfer reaction, the triply H‐bonded trimer formation of 6‐azaindole and its ESTPT reaction are demonstrated.
Trinity Roots: 6‐azaindole undergoes self‐assembly by formation of N(1)−H⋅⋅⋅N(6) hydrogen bonds (H bonds), to form a cyclic, triply H‐bonded trimer. The H‐bonded trimer undergoes excited‐state triple proton transfer (ESTPT), resulting in a proton‐transfer tautomer emission maximized at 435 nm.
A new coordination polymer, Zn(HBTC)(BPE)0.5(H2O) n ·nH2O (1) with an extended 1D ladderlike metal−organic framework (MOF) has been synthesized and structural characterized by single-crystal X-ray ...diffraction method. Structural determination reveals that, in compound 1, the Zn(II) ion is four-coordinated in a distorted tetrahedral geometry, bonded to one nitrogen atom from one BPE ligand, and three oxygen atoms from two monodentate carboxylate groups of two HBTC2− ligands and one coordinated water molecule. The HBTC2− acts as a bridging ligand with a bis-monodentate coordination mode, connecting the Zn(II) ions to form a one-dimensional (1D) Zn(HBTC) chain. Two 1D chains are then interlinked via the connectivity between the ZnII ions and anti-BPE liagnds to complete the 1D ladderlike MOF. Adjacent 1D Ladders are further extended to a 2D hydrogen-bonded layered network through the intermolecular O−H···O hydrogen bond between the carboxylic group and carboxylate group of interladder HBTC2− ligand. Adjacent 2D layers are then packed orderly in an ABAB-type array via the intermolecular interactions of combined π−π interaction and O−H···O hydrogen bonds to form a 3D supramolecular architecture exhibiting 1D channels intercalated with guest water molecules. The reversible solid-state structural transformation between crystalline 1 with 1D ladderlike framework and its dehydrated powder 2, Zn(HBTC)(BPE)0.5 n , with 2D framework via the displacement of coordinated water molecule to HBTC2− ligand, by thermal de/rehydrated processes has been verified by PXRD measurements. The emission of 1 and 2 is ascribed to a ligand-based transition.
A new coordination polymer, Zn(dpe)(bdc)⋅4H2O (ZndB; dpe=1,2‐bis(4‐pyridyl)ethane, bdc2−=dianion of benzenedicarboxylic acid), which possesses a 3D metal–organic framework (MOF) has been synthesized ...and structurally characterized. This 3D MOF is constructed by the assembly of helical channels filled with guest water molecules in both inner and outer regions of the channel. The resulting network also creates a 2D water layer containing hydrogen‐bonded (H2O)16 rings as the basic building units. Thermogravimetric and powder X‐ray diffraction measurements of ZndB revealed a two‐step weight loss of water molecules with a reversible water adsorption/desorption process in the inner channel for the first stage, and irreversible water desorption in the outer channel for the second stage. This spongelike property is manifested by the excimer emission originating from interaction between dpe (π*) and the other dpe (π) of the proximal helical channel, which is highly sensitive to the environmental perturbation. Powder X‐ray analyses reveal that the dehydration process induces the readjustment of dpe π–π stacking distance/orientation, which results in dramatic luminescence changes from dim pale blue (λem≈470 nm) upon hydration to bright white‐light generation (broad, λem≈500–550 nm) upon water depletion, accompanied by a ≈100‐fold increase in the emission intensity.
Holding water: Zn(dpe)(bdc)⋅4H2O (ZndB; dpe=1,2‐bis(4‐pyridyl)ethane, bdc2−=dianion of benzenedicarboxylic acid) has a 3D metal–organic framework constructed by the assembly of helical channels filled with guest water molecules. The resulting network creates a 2D water layer containing hydrogen‐bonded (H2O)16 rings. Color changes occur upon hydration and water depletion of ZndB, accompanied by an increase in emission intensity (see figure).
PtFe alloy nanostructures enclosed by differently oriented facets, including polyhedrons, concave cubes, and nanocubes, were synthesized through the fine adjustment of specific surfactant–crystal ...facet bindings. PtFe nanostructures with various alloy compositions were then employed as the counter electrodes (CEs) for the redox reaction of iodide/tri-iodide (I–/I3 –) in dye-sensitized solar cells. Devices with the Pt9Fe1 polyhedrons and Pt9Fe1 concave cubes produced better photovoltaic conversion efficiency (PCE) of 8.01% and 7.63% in comparison to the PCE of 7.24% achieved with Pt CE. The superiority is attributed to the rapid charge transfer, higher limit current, and better electronic conductivity and catalytic activity with respect to the Pt CEs. The photovoltaic and electrochemical results indicated the shape- and composition-dependent activity in the I–/I3 – redox reaction, which obeys the sequence of polyhedrons > concave cubes > nanocubes and Pt9Fe1 nanostructures > Pt7Fe3 nanostructures. Further theoretical work indicated that the I3 – reduction activity of the nanosurfaces was in the order of Pt9Fe1(111) > Pt(111) > Pt9Fe1(100). The combination of experimental and theoretical work thus clearly demonstrates the shape- and composition-dependence of PtFe nanostructures in terms of the I3 – reduction activity.
Molecular self-assembly, taking advantage of reversible intermolecular interactions, represents an efficient method to prepare ultrathin films exhibiting minimal packing defects. The same protocol ...seems reasonable to fabricate hybrid monolayers yet typically results in segregated domains. Demonstrated herein is a host–guest concept in which guest molecules are hosted in homogeneously patterned voids at the liquid–solid interface. However, 2D open lattices with low packing densities often suffer poor stability. In this study, the concept is realized by a 2D porous network assembled via 1,3,5-tris(4-carboxyphenyl)benzene (BTB) whose stability is significantly enhanced by hosting spatially matched pentacene or its analogues. The conformal contact between the nearest neighbors optimizes intermolecular interactions. Simulation results of molecular mechanics for a simplified model suggest that the hybrid lattice is about 250 kcal/mol per BTB pore more stable than guests such as coronene and Cu-phthalocyanine.
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