Component-controlled synthesis of PdxSny nanocrystals on carbon nanotubes as advanced electrocatalysts for oxygen reduction reaction.

Pd-based bimetallic or multimetallic nanocrystals are considered to be potential electrocatalysts for cathodic oxygen reduction reaction (ORR) in fuel cells. Although much advance has been made, the synthesis of component-controlled Pd-Sn alloy nanocrystals or corresponding nanohybrids is still challenging, and the electrocatalytic ORR properties are not fully explored. Herein, component-controlled synthesis of PdxSny nanocrystals (including Pd3Sn, Pd2Sn, Pd3Sn2, and PdSn) has been realized, which are in situ grown or deposited on pre-treated multi-walled carbon nanotubes (CNTs) to form well-coupled nanohybrids (NHs) by a facile one-pot non-hydrolytic system thermolysis method. In alkaline media, all the resultant PdxSny/CNTs NHs are effective at catalyzing ORR. Among them, the Pd3Sn/CNTs NHs exhibit the best catalytic activity with the half-wave potential of 0.85 V (vs. RHE), good cyclic stability, and excellent methanol-tolerant capability due to the suited Pd-Sn alloy component and its strong interaction or efficient electronic coupling with CNTs. This work is conducive to the advancement of Pd-based nanoalloy catalysts by combining component engineering and a hybridization strategy and promoting their application in clean energy devices.

Porous Flower-Like Nanoarchitectures Derived from Nickel Phosphide Nanocrystals Anchored on Amorphous Vanadium Phosphate Nanosheet Nanohybrids for Superior Overall Water Splitting.

Transition metal phosphides (TMPs) and phosphates (TM-Pis) nanostructures are promising functional materials for energy storage and conversion. Nonetheless, controllable synthesis of crystalline/amorphous heterogeneous TMPs/TM-Pis nanohybrids or related nanoarchitectures remains challenging, and their electrocatalytic applications toward overall water splitting (OWS) are not fully explored. Herein, the Ni2P nanocrystals anchored on amorphous V-Pi nanosheet based porous flower-like nanohybrid architectures that are self-supported on carbon cloth (CC) substrate (Ni2P/V-Pi/CC) are fabricated by conformal oxidation and phosphorization of pre-synthesized NiV-LDH/CC. Due to the unique microstructures and strong synergistic effects of crystalline Ni2P and amorphous V-Pi components, the obtained Ni2P/V-Pi/CC owns abundant active sites, suitable surface/interface electronic structure and optimized adsorption-desorption of reaction intermediates, resulting in outstanding electrocatalytic performances toward hydrogen and oxygen evolution reactions in alkaline media. Correspondingly, the assembled Ni2P/V-Pi/CC||Ni2P/V-Pi/CC electrolyzer only needs an ultralow cell voltage (1.44 V) to deliver 10 mA cm-2 water-splitting currents, exceeding its counterparts, recently reported bifunctional catalysts-based devices, and Pt/C/CC||IrO2/CC pairs. Moreover, the Ni2P/V-Pi/CC||Ni2P/V-Pi/CC manifests remarkable stability. Also, such device shows a certain prospect for OWS in acidic media. This work may spur the development of TMPs/TMPis-based nanohybrid architectures by combining structure and phase engineering, and push their applications in OWS or other clean energy options.

Amorphous Ni-Fe-Mo Oxides Coupled with Crystalline Metallic Domains for Enhanced Electrocatalytic Oxygen Evolution by Promoted Lattice-Oxygen Participation.

The crystalline/amorphous heterophase nanostructures are promising functional materials for biomedicals, catalysis, energy conversion, and storage. Despite great progress is achieved, facile synthesis of crystalline metal/amorphous multinary metal oxides nanohybrids remains challenging, and their electrocatalytic oxygen evolution reaction (OER) performance along with the catalytic mechanism are not systematically investigated. Herein, two kinds of ultrafine crystalline metal domains coupled with amorphous Ni-Fe-Mo oxides heterophase nanohybrids, including Ni/Ni0.5-a Fe0.5 Mo1.5 Ox and Ni-FeNi3 /Ni0.5-b Fe0.5-y Mo1.5 Ox , are fabricated through controllable reduction of amorphous Ni0.5 Fe0.5 Mo1.5 Ox precursors by simply tuning the amount of used reductant. Due to the suited component in metal domains, the special structure with dense crystalline/amorphous interfaces, and strong electronic coupling of their components, the resultant Ni-FeNi3 /Ni0.5-b Fe0.5-y Mo1.5 Ox nanohybrids show greatly enhanced OER activity with a low overpotential (278 mV) to reach 10 mA cm-2 current density and ultrahigh turnover frequency (38160 h-1 ), outperforming Ni/Ni0.5-a Fe0.5 Mo1.5 Ox , Ni0.5 Fe0.5 Mo1.5 Ox precursors, commercial IrO2 , and most of recently reported OER catalysts. Also, such Ni-FeNi3 /Ni0.5-b Fe0.5-y Mo1.5 Ox nanohybrids manifest good catalytic stability. As revealed by a series of spectroscopy and electrochemical analyses, their OER mechanism follows the lattice-oxygen-mediated (LOM) pathway. This work may shed light on the design of advanced heterophase nanohybrids, and promote their applications in water splitting, metal-air batteries, or other clean energy fields.

Large-Scale Synthesis of Hierarchical Porous MOF Particles via a Gelation Process for High Areal Capacitance Supercapacitors.

Metal-organic frameworks (MOFs) with hierarchical porous structures have been attracting intense interest currently due to their promising applications in catalysis, energy storage, drug delivery, and photocatalysis. Current fabrication methods usually employ template-assisted synthesis or thermal annealing at high temperatures. However, large-scale production of hierarchical porous metal-organic framework (MOF) particles with a simple procedure and mild condition is still a challenge, which hampers their application. To address this issue, we proposed a gelation-based production method and achieved hierarchical porous zeolitic imidazolate framework-67 (called HP-ZIF67-G thereafter) particles conveniently. This method is based on a metal-organic gelation process through a mechanically stimulated wet chemical reaction of metal ions and ligands. The interior of the gel system is composed of small nano and submicron ZIF-67 particles as well as the employed solvent. The relatively large pore size of the graded pore channels spontaneously formed during the growth process is conducive to the increased transfer rate of substances within the particles. It is proposed that the Brownian motion amplitude of the solute is greatly reduced in the gel state, which leads to porous defects inside the nanoparticles. Furthermore, HP-ZIF67-G nanoparticles interwoven with polyaniline (PANI) exhibited an exceptional electrochemical charge storage performance with an areal capacitance of 2500 mF cm-2, surpassing those of many MOF materials. This stimulates new studies on MOF-based gel systems to obtain hierarchical porous metal-organic frameworks which should benefit further applications in a wide spectrum of fields ranging from fundamental research to industrial applications.

Phase-Controlled Synthesis of Nickel-Iron Nitride Nanocrystals Armored with Amorphous N-Doped Carbon Nanoparticles Nanocubes for Enhanced Overall Water Splitting.

Transition metal nitrides (TMNs) nanostructures possess distinctive electronic, optical, and catalytic properties, showing great promise to apply in clean energy, optoelectronics, and catalysis fields. Nonetheless, phase-regulation of NiFe-bimetallic nitrides nanocrystals or nanohybrid architectures confronts challenges and their electrocatalytic overall water splitting (OWS) performances are underexplored. Herein, novel pure-phase Ni2+ x Fe2- x N nanocrystals armored with amorphous N-doped carbon (NC) nanoparticles nanocubes (NPNCs) are obtained by controllable nitridation of NiFe-Prussian-blue analogues derived oxides/NC NPNCs under Ar/NH3 atmosphere. Such Ni2+ x Fe2- x N/NC NPNCs possess mesoporous structures and show enhanced electrocatalytic activity in 1 m KOH electrolyte with the overpotential of 101 and 270 mV to attain 10 and 50 mA cm-2 current toward hydrogen and oxygen evolution reactions, outperforming their counterparts (mixed-phase NiFe2 O4 /Ni3 FeN/NC and NiFe oxides/NC NPNCs). Remarkably, utilizing them as bifunctional catalysts, the assembled Ni2+ x Fe2- x N/NC||Ni2+ x Fe2- x N/NC electrolyzer only needs 1.51 V cell voltage for driving OWS to approach 10 mA cm-2 water-splitting current, exceeding their counterparts and the-state-of-art reported bifunctional catalysts-based devices, and Pt/C||IrO2 couples. Additionally, the Ni2+ x Fe2- x N/NC||Ni2+ x Fe2- x N/NC manifests excellent durability for OWS. The findings presented here may spur the development of advanced TMNs nanostructures by combining phase, structure engineering, and hybridization strategies and stimulate their applications toward OWS or other clean energy fields.

Signal Filtering Enabled by Spike Voltage-Dependent Plasticity in Metalloporphyrin-Based Memristors.

Neural systems can selectively filter and memorize spatiotemporal information, thus enabling high-efficient information processing. Emulating such an exquisite biological process in electronic devices is of fundamental importance for developing neuromorphic architectures with efficient in situ edge/parallel computing, and probabilistic inference. Here a novel multifunctional memristor is proposed and demonstrated based on metalloporphyrin/oxide hybrid heterojunction, in which the metalloporphyrin layer allows for dual electronic/ionic transport. Benefiting from the coordination-assisted ionic diffusion, the device exhibits smooth, gradual conductive transitions. It is shown that the memristive characteristics of this hybrid system can be modulated by altering the metal center for desired metal-oxygen bonding energy and oxygen ions migration dynamics. The spike voltage-dependent plasticity stemming from the local/extended movement of oxygen ions under low/high voltage is identified, which permits potentiation and depression under unipolar different positive voltages. As a proof-of-concept demonstration, memristive arrays are further built to emulate the signal filtering function of the biological visual system. This work demonstrates the ionic intelligence feature of metalloporphyrin and paves the way for implementing efficient neural-signal analysis in neuromorphic hardware.

Cu,N-Codoped Carbon Nanodisks with Biomimic Stomata-Like Interconnected Hierarchical Porous Topology as Efficient Electrocatalyst for Oxygen Reduction Reaction.

Metal,N-codoped carbon (M-N-C) nanostructures are promising electrocatalysts toward oxygen reduction reaction (ORR) or other gas-involved energy electrocatalysis. Further creating pores into M-N-C nanostructures can increase their surface area, fully expose the active sites, and improve mass transfer and electrocatalytic efficiency. Nonetheless, it remains a challenge to fabricate M-N-C nanomaterials with both well-defined morphology and hierarchical porous structures. Herein, high-quality 2D Cu-N-C nanodisks (NDs) with biomimic stomata-like interconnected hierarchical porous topology are synthesized via carbonization of Cu-tetrapyridylporphyrin (TPyP)-metal-organic frameworks (MOFs) precursors and followed by etching the carbonization product (Cu@Cu-N-C) along with re-annealing treatment. Such hierarchical porous Cu-N-C NDs possess high specific surface area (293 m2 g-1 ) and more exposed Cu single-atom sites, different from their counterparts (Cu@Cu-N-C) and pure N-C control catalysts. Electrochemical tests in alkaline media reveal that they can efficiently catalyze ORR with a half-wave potential of 0.85 V (vs reversible hydrogen electrode), comparable to Pt/C and outperforming Cu@Cu-N-C, N-C, Cu-TPyP-MOFs, and most other reported M-N-C catalysts. Moreover, their stability and methanol-tolerant capability exceed Pt/C. This work may shed some light on optimizing 2D M-N-C nanostructures through bio-inspired pore structure engineering, and accelerate their applications in fuel cells, artificial photosynthesis, or other advanced technological fields.

Cobalt Phosphides Nanocrystals Encapsulated by P-Doped Carbon and Married with P-Doped Graphene for Overall Water Splitting.

As one class of important functional materials, transition metal phosphides (TMPs) nanostructures show promising applications in catalysis and energy storage fields. Although great progress has been achieved, phase-controlled synthesis of cobalt phosphides nanocrystals or related nanohybrids remains a challenge, and their use in overall water splitting (OWS) is not systematically studied. Herein, three kinds of cobalt phosphides nanocrystals encapsulated by P-doped carbon (PC) and married with P-doped graphene (PG) nanohybrids, including CoP@PC/PG, CoP-Co2 P@PC/PG, and Co2 P@PC/PG, are obtained through controllable thermal conversion of presynthesized supramolecular gels that contain cobalt salt, phytic acid, and graphene oxides at proper temperature under Ar/H2 atmosphere. Among them, the mixed-phase CoP-Co2 P@PC/PG nanohybrids manifest high electrocatalytic activity toward both hydrogen and oxygen evolution in alkaline media. Remarkably, using them as bifunctional catalysts, the fabricated CoP-Co2 P@PC/PG||CoP-Co2 P@PC/PG electrolyzer only needs a cell voltage of 1.567 V for driving OWS to reach the current density at 10 mA cm-2 , superior to their pure-phase counterparts and recently reported bifunctional catalysts based devices. Also, such a CoP-Co2 P@PC/PG||CoP-Co2 P@PC/PG device exhibits outstanding stability for OWS. This work may shed some light on optimizing TMPs nanostructures based on phase engineering, and promote their applications in OWS or other renewable energy options.

Well-Coupled Nanohybrids Obtained by Component-Controlled Synthesis and in Situ Integration of Mn xPd y Nanocrystals on Vulcan Carbon for Electrocatalytic Oxygen Reduction.

Development of cheap, highly active, and robust bimetallic nanocrystal (NC)-based nanohybrid (NH) electrocatalysts for oxygen reduction reaction (ORR) is helpful for advancing fuel cells or other renewable energy technologies. Here, four kinds of well-coupled Mn xPd y(MnPd3, MnPd-Pd, Mn2Pd3, Mn2Pd3-Mn11Pd21)/C NHs have been synthesized by in situ integration of Mn xPd y NCs with variable component ratios on pretreated Vulcan XC-72 C using the solvothermal method accompanied with annealing under Ar/H2 atmosphere and used as electrocatalysts for ORR. Among them, the MnPd3/C NHs possess the unique "half-embedded and half-encapsulated" interfaces and exhibit the highest catalytic activity, which can compete with some currently reported non-Pt catalysts (e.g., Ag-Co nanoalloys, Pd2NiAg NCs, PdCo/N-doped porous C, G-Cu3Pd nanocomposites, etc.), and close to commercial Pt/C. Electrocatalytic dynamic measurements disclose that their ORR mechanism abides by the direct 4e- pathway. Moreover, their durability and methanol-tolerant capability are much higher than that of Pt/C. As revealed by spectroscopic and electrochemical analyses, the excellent catalytic performance of MnPd3/C NHs results from the proper component ratio of Mn and Pd and the strong interplay of their constituents, which not only facilitate to optimize the d-band center or the electronic structure of Pd but also induce the phase transformation of MnPd3 active components and enhance their conductivity or interfacial electron transfer dynamics. This work demonstrates that MnPd3/C NHs are promising methanol-tolerant cathode electrocatalysts that may be employed in fuel cells or other renewable energy option.

SMART Design of a Bulk-Capped Supramolecular Segment for the Assembly into Organic Interdigital Lipid Bilayer-Like (ILB) Nanosheets.

Rational molecular design for the organic nanocrystal morphology still remains a challenge due to the structural diversity and complicated weak intermolecular interactions. In this work, a typical attractor-repulsor molecule N,N-diphenyl-4-(9-phenyl-fluoren-9-yl) phenylamine (TPA-PF) is designed to explore a general assembly strategy for 2D nanocrystals. Via an interdigital lipid bilayer-like (ILB) molecular packing mode, large-sized lamellar 2D nanosheets are obtained with a length:width:thickness ratio as ≈2500:1000:1. The d-spacing of the largest (001) plane is 1.32 nm, which equals to the thickness of a single interdigital stacking layer. The synergetic effect of the attractive supramolecular segment (TPA) and the repulsive bulky group (PF) is supposed to be the critical factor for the ILB packing that leads to the 2D structures. The attractor-repulsor molecule design is expected to be an effective strategy for the growth of 2D nanocrystals based on small organic molecules.

Coralloid Co2P2O7 Nanocrystals Encapsulated by Thin Carbon Shells for Enhanced Electrochemical Water Oxidation.

Core-shell nanohybrids containing cheap inorganic nanocrystals and nanocarbon shells are promising electrocatalysts for water splitting or other renewable energy options. Despite that great progress has been achieved, biomimetic synthesis of metal phosphates@nanocarbon core-shell nanohybrids remains a challenge, and their use for electrocatalytic oxygen evolution reaction (OER) has not been explored. In this paper, novel nanohybrids composed of coralloid Co2P2O7 nanocrystal cores and thin porous nanocarbon shells are synthesized by combination of the structural merits of supramolecular polymer gels and a controllable thermal conversion technique, i.e., temperature programmable annealing of presynthesized supramolecular polymer gels that contain cobalt salt and phytic acid under a proper gas atmosphere. Electrocatalytic tests in alkaline solution show that such nanohybrids exhibit greatly enhanced electrocatalytic OER performance compared with that of Co2P2O7 nanostructure. At a current density of 10 mA cm(-2), their overpotential is 0.397 V, which is much lower than that of Co2P2O7 nanostructures, amorphous Co-Pi nanomaterials, Co(PO3)2 nanosheets, Pt/C, and some reported OER catalysts, and close to that of commercial IrO2. Most importantly, both of their current density at the overpotential over 0.40 V and durability are superior to those of IrO2 catalyst. As revealed by a series of spectroscopic and electrochemical analyses, their enhanced electrocatalytic performance results from the presence of thin porous nanocarbon shells, which not only improve interfacial electron penetration or transfer dynamics but also vary the coordination environment and increase the number of active 5-coordinated Co(2+) sites in Co2P2O7 cores.

Kinetically controlled assembly of a spirocyclic aromatic hydrocarbon into polyhedral micro/nanocrystals.

Nonplane molecules with multiple large aromatic planes could be promising candidates to form various polyhedral micro/nanocrystals by manipulating the different π···π stacking, tuning the cohesive energies of crystal facets, and controlling the kinetic growth process. Spirocyclic aromatic hydrocarbons (SAHs) not only have two cross-shaped aromatic planes but also offer the feature of supramolecular steric hindrance, making it favorable for the heterogeneous kinetic growth into highly symmetric polyhedra. Herein, we report that a novel SAH compound, spiro[fluorene-9,7'-dibenzo[c,h]acridine]-5'-one (SFDBAO), can self-assemble into various monodispersed shapes such as hexahedra, octahedra, and decahedra through the variation of either different types of surfactants, such as Pluronic 123 (P123) and cetyltrimethyl ammonium bromide (CTAB), or growth parameters. In addition, the possible mechanism of crystal facet growth has been proposed according to the SEM, XRD, TEM, and SAED characterization of organic polyhedral micro/nanocrystals. The unique cruciform-shaped SAHs have been demonstrated as fascinating supramolecular synthons for various highly symmetric polyhedral assembling.

A small change in molecular structure, a big difference in the AIEE mechanism.

An anthracene carboxamide derivative of the excited-state intramolecular proton-transfer compound of 2-(2'-hydroxyphenyl)benzothiazole has been newly developed to produce the prominent characteristics of aggregation-induced enhanced emission (AIEE) with a high solid-state fluorescence quantum efficiency of 78.1%. Compared with our previously reported phenyl carboxamide derivatives, a small tailoring of the molecular structure was found to result in a big difference in the dominant factor of the AIEE mechanism. In the phenyl carboxamide derivatives, the dominant factor of the AIEE mechanism is the restriction of the twisted intramolecular charge transfer (TICT) of the enol excited state, regardless of their different aggregation modes. In the anthracene carboxamide derivative, N-(3-(benzo[d]thiazol-2-yl)-4-hydroxyphenyl) anthracene-9-carboxamide, the AIEE characteristics are not dependent on the restriction of TICT, but mainly attributed to the cooperative effects of J-aggregation and the restriction of the cis-trans tautomerization in the keto excited state. A specific N···π interaction was found to be the main driving force for this J-aggregation, as revealed by the single crystal analysis. The AIEE mechanism of this anthracene carboxamide derivative was studied in detail through photophysical investigations and theoretical calculations. On the basis of its AIEE characteristics, a stable non-doped organic light-emitting diode was achieved, with high color purity and a remarkably low efficiency roll-off.

Facile synthesis of shape and size tunable porphyrinoid coordination polymers: from copper porphyrin nanoplates to microspindles.

Size tunable copper porphyrin dispersed nanoplates, assembled nanoplates, and microspindles have been controllably fabricated by a simple surfactant-assisted solution route.

Tuning the optoelectronic properties of 4,4'-N,N'-dicarbazole-biphenyl through heteroatom linkage: new host materials for phosphorescent organic light-emitting diodes.

Five carbazole end-capped heterofluorenes (CzHFs) designed by structurally mimicking 4,4'-N,N'-dicarbazole-biphenyl (CBP) via connecting the biphenyl core of CBP with the linking atom of C, P, N, O, and S, respectively, were synthesized successfully, and their optoelectronic properties were investigated. The theoretical calculations and experimental results demonstrate that CzHFs are potential green, red, and even blue hosts for phosphorescent light-emitting diodes (PHOLEDs) with more desirable localization and energy levels of HOMO and LUMO and also higher triplet energy than CBP.

Anions bonded on the supramolecular hydrogel surface as the growth center of biominerals.

In this work, a supramolecular hydrogel formed from N,N',N''-tris(3-pyridyl)-trimesic amide was reported to serve as the matrix for the growth of biominerals. The organic hydrogel scaffold contains nitrogen heterocyclic ring and amide groups that can bind anions of the mineral (specially here, carbonate ions and phosphate ions) through hydrogen bonding interactions and act as the biomineralization active sites for growing biominerals. Calcium carbonate nucleated on the site of the hydrogel fiber where carbonate ions bonded and left obvious hydrogel fiber prints on the obtained product. Calcium phosphate grew into curved platelike nanostructures along the hydrogel fibrous network. XRD pattern and FT-IR spectra confirmed the formation of minerals on the hydrogel. The results indicate that the hydrogen bonding interaction can provide strong enough binding force for the growth of the minerals on organic scaffolds. Our finding extends the organic scaffolds into biodegradable small molecule hydrogels and also extends the growth centers of the minerals from conventional carboxylate groups binding Ca(2+) to amide and pyridyl groups binding PO(4)(3-).

Self-assembly of two different hierarchical nanostructures on either side of an organic supramolecular film in one step.

We fabricated different hierarchical organic nanostructures on each side of a supramolecular film, by using hydrogen-bonding interactions between tetrapyridylporphyrin and benzene-1,3,5-tricarboxylic acid at the H2O/CHCl3 interface. The surface of the film that faces water is composed of nanoprism arrays, whereas the surface facing CHCl3 is composed of three-dimensional sunflower-like hierarchical micro- and nanostructures. FTIR spectral evidence showed that all pyridyl groups of the tetrapyridylporphyrin hydrogen bonded to the carboxylic acid groups of 1,3,5-benzene-tricarboxylic acid. The aggregation modes of porphyrin presented in this supramolecular film were studied by UV/Vis and fluorescence spectroscopy. Moreover, each side of the film exhibits distinct soakage properties.

Large-scale synthesis of single-crystalline RE2O3 (RE=Y, Dy, Ho, Er) nanobelts by a solid-liquid-phase chemical route.

Yttrium-group heavy rare-earth sesquioxide (RE(2)O(3), RE=Y, Dy, Ho, Er) nanobelts were successfully fabricated by thermolysis of solid RE(NO(3))(3)x H(2)O in a dodecylamine/1-octadecene mixed solvent system. The synthetic principle is based on separating the nucleation and growth processes by utilizing the poor solubility of RE(NO(3))(3)chi H(2)O in the solvent mixture and the heat-transportation difference between the liquid and solid. By using dodecylamine, RE(2)O(3) nanobelts can be readily obtained. X-ray diffraction (XRD) analysis shows that the synthesized RE(2)O(3) nanobelts are body-centered cubic and crystalline. Field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), selective-area electron diffraction (SAED), and high-resolution transmission electron microscopy (HR-TEM) demonstrate that the synthesized RE(2)O(3) compounds possess regular geometric structure (beltlike) with perfect crystallinity. Preliminary experimental results prove that the dodecylamine plays a key role in the formation of RE(2)O(3) nanobelts and cannot be replaced by other surfactants. Furthermore, this method can be extended to the synthesis of RE(2)O(3) nanobelt/metal nanocrystal nanocomposites and ABO(3) (A=Y, Dy, Ho, Er; B=Al) and A(3)B(5)O(12) (A=Y, Dy, Ho, Er; B=Al)-type ternary oxide nanobelts, using mixed-metal nitrate salts in the correct stoichiometry instead of single rare-earth nitrates.