Novel metalloporphyrin covalently functionalized polyphosphazene nanotubes for boosting the hydrogen evolution reaction.

Herein, we demonstrate the first example of a novel electrocatalytic hybrid system (CoTPP-PZSNT) with a push-pull motif to boost hydrogen evolution reaction (HER) activity. CoTPP-PZSNT exhibits an efficient HER activity, with overpotentials of 157 and 109 mV at 10 mA cm-2 in 1.0 M KOH and 0.5 M H2SO4 solutions, respectively. The HER performance of CoTPP-PZSNT outperforms many previously reported HER catalysts, due to efficient charge transfer between each component.

Acenaphthenediimine complex-bridged porphyrin porous organic polymer with enriched active sites as a robust water splitting electrocatalyst.

To realize efficient water splitting, a highly promising hydrogen evolution reaction (HER) electrocatalyst is needed for the generation of hydrogen. Herein, we demonstrate a novel acenaphthenediimine complex-bridged porphyrin porous organic polymer (NiTAPP-NiACQ) with enriched active metal sites and hierarchical pores. The as-prepared NiTAPP-NiACQ exhibits good long-term durability and remarkable HER performance in 1.0 M KOH with a low overpotential of 117 mV at 10 mA cm-2, which is comparable to many previously reported electrocatalytic HER systems. Furthermore, a simple water-alkali electrolyzer using NiTAPP-NiACQ as the cathode requires a small cell voltage of 1.59 V to deliver a current density of 10 mA cm-2 at room temperature, along with outstanding durability. NiTAPP-NiACQ features not only a metal ion as the catalytic active center in the porphyrin core but also metal ion coordination on the anthraquinone component to promote HER performance, enabling multiple metal ions as the electrocatalytic active sites for the HER reaction. The excellent HER activity of NiTAPP-NiACQ is ascribed to a combination of mechanisms. These findings highlight the viability of porphyrin-derived porous organic polymers in energy conversion processes.

Efficient oxygen evolution reaction from iron-molybdenum nitride/molybdenum oxide heterostructured composites.

Integrating various active sites into a multi-component system might significantly enhance the oxygen evolution reaction (OER) performance. Herein, the as-prepared iron-molybdenum nitride/molybdenum oxide (Fe-Mo5N6/MoO3-550) composite electrocatalyst under optimum conditions demonstrates excellent electrocatalytic performance toward OER and reaches current densities of 10 and 20 mA cm-2 at overpotentials of 201 and 216 mV, respectively. The OER performance of Fe-Mo5N6/MoO3-550 exceeds that of most previously reported electrocatalytic systems. The significant improvement in the OER performance is ascribed to a combination of mechanisms. The strong electronic interactions among the Fe, Mo5N6 and MoO3 species can accelerate the OER reaction kinetics, which contributes to the OER performance. This work provides new insights into the construction of efficient electrocatalytic materials with inexpensive metals.

Boosted hydrogen evolution reaction for a nitrogen-rich azo-bridged metallated porphyrin network.

The potential of porous organic polymers (POPs) toward electrocatalytic water splitting have attracted considerable scientific attention, due to their high specific surface areas, superlative porosity and diverse electronic structures; yet it remains challenging. Herein, we report a facile synthesized novel nitrogen-rich azo-bridged metallated porphyrin POP (CoTAPP-CoTNPP) for improving the hydrogen evolution reaction (HER) activity. The incorporation of the cobalt porphyrins and the azo groups endows CoTAPP-CoTNPP with effective charge transfer efficiency and large π-conjugated porous frameworks, thus enhancing the HER performance. Origins of the excellent HER performance of the material are evaluated using a series of structural and electrochemical measurements. Remarkably, CoTAPP-CoTNPP exhibits low overpotentials of 103 and 170 mV to reach 10 mA cm-2 in acidic and alkaline media, respectively, outperforming many previously reported HER electrocatalysts. These results demonstrate the enormous potential of the as-prepared azo-linked porphyrin POP for electrocatalytic water splitting.

Efficient hydrogen generation of a cobalt porphyrin-bridged covalent triazine polymer.

Hydrogen production obtained by electrocatalytic water splitting exhibits great promise in addressing both energy shortage and environmental contamination. Herein, we prepared a novel cobalt porphyrin (CoTAPP)-bridged covalent triazine polymer (CoTAPPCC) by covalently linking CoTAPP with cyanuric chloride (CC) for catalytic hydrogen evolution reaction (HER). Both experimental techniques and density functional theory (DFT) calculations were used to evaluate the correlation of HER activity with molecular structures. Benefiting from the strong electronic interactions between the CC unit and the CoTAPP moiety, a standard current density at 10 mA cm-2 is obtained for CoTAPPCC with a low overpotential of 150 mV in acid, which is comparable to or better than the best records reported previously. Additionally, a competitive HER activity in basic medium is obtained for CoTAPPCC. The strategy reported herein is valuable for designing and developing porphyrin-based efficient HER electrocatalysts.

Synergistic catalysis of graphitic carbon nitride supported bimetallic sulfide nanostructures for efficient oxygen generation.

Herein, a series of g-C3N4 supported bimetallic sulfide nanostructures (Ni3S2/MoS2/ng-C3N4, n = 10, 20 and 30) was prepared by a hydrothermal method and subsequently a thermal annealing approach. Ni3S2/MoS2/20g-C3N4 with controlled composition exhibits efficient OER activity with a low overpotential of 183 mV at 10 mA cm-2, which outperforms the vast majority of sulfide OER electrocatalysts reported previously.

A tin porphyrin axially-coordinated two-dimensional covalent organic polymer for efficient hydrogen evolution.

Herein, we demonstrate a facile strategy for constructing an efficient and stable hydrogen evolution reaction (HER) catalyst, i.e. a tin porphyrin axially-coordinated 2D covalent organic polymer (SnTPPCOP). SnTPPCOP exhibits promising HER activity with a low overpotential of 147 mV at 10 mA cm-2 due to its unique structural properties, ranking among the best records reported recently.

Strongly Coupled Nitrogen-Doped Mo2C@CoNi Alloy Hybrid Architecture toward Efficient Hydrogen Evolution Reaction.

Development of high-efficiency electrocatalysts for water splitting is a promising channel to produce clean hydrogen energy. Herein, we demonstrate that the combination of nitrogen-doped Mo2C and CoNi alloy to form a hybrid architecture is an effective way to produce hydrogen from electrochemical water splitting. Benefiting from a combination of mechanisms, the optimized N-Mo2C@CoNi-650 shows remarkable hydrogen evolution reaction (HER) activity with small overpotentials of 35, 123, and 220 mV to reach the current density of 10, 50, and 100 mA cm-2 in alkaline media, respectively, outperforming most previously reported HER electrocatalysts. The efficient electrocatalytic performance is ascribed to the highly exposed active sites, fast reaction kinetics, and improved charge-transfer steaming from the synergistic effect between each component. This work presents a new insight into designing and preparing highly efficient electrocatalysts toward the HER.

Synergistic optimization promoted overall water splitting of CoSe@NiSe2@MoS2 heterostructured composites.

Herein, the preparation of CoSe@NiSe2@MoS2 composites and the systematic investigation of their water splitting performance as a function of composition have been demonstrated. CoSe@NiSe2@MoS2-12 with the optimized composition exhibits a current density of 10 mA cm-2 at overpotentials of 81 and 170 mV for HER and OER in alkaline conditions, respectively. The overall water splitting device built using CoSe@NiSe2@MoS2-12 exhibited a low voltage of 1.48 V at 10 mA cm-2 due to the synergistic effects.

Enhanced optical limiting and hydrogen evolution of graphene oxide nanohybrids covalently functionalized by covalent organic polymer based on porphyrin.

Herein, we report a novel graphene oxide (GO) nanohybrid covalently functionalized by covalent organic polymer (COP) based on porphyrin (GO-TPPCOP), as the optical limiter and hydrogen evolution reaction (HER) electrocatalyst. The GO-TPPCOP nanohybrid exhibits markedly enhanced optical limiting and HER activity over that of TPP, GO and TPPCOP alone. More importantly, the optical limiting property and HER activity of GO-TPPCOP nanohybrid are comparable to the state-of-the-art activity of materials from some previous reports. The possible mechanisms of optical limiting and HER are explored by various means, including UV-Vis absorption, fluorescence, photocurrent, electrochemical impedance spectra and Raman spectroscopic techniques. It is demonstrated that the synergistic effect and charge transfer between GO and TPPCOP are important factors in determining its optical limiting and HER performances. These results demonstrate a new strategy to design and develop functional nanohybrids for efficient optical limiting and HER activity by the covalent linkage of GO with COPs.

Rational design of FeOx-MoP@MWCNT composite electrocatalysts toward efficient overall water splitting.

Herein, a series of FeOx-MoP@MWCNT composite electrocatalysts was designed and prepared to investigate the influence of the content of FeOx on the water splitting performance. The optimized FeOx-MoP@MWCNTs-2 exhibits excellent hydrogen and oxygen evolution reaction activity while a cell voltage of 1.51 V with outstanding stability is attained, attributed to the synergistic effect of each component, as evidenced by the experimental and density functional theory results. The observed electrocatalytic activity outperforms current state-of-the-art non-precious metal electrocatalysts.

Electrochemical hydrogen and oxygen evolution reactions from a cobalt-porphyrin-based covalent organic polymer.

Covalent organic polymers have attracted much attention due to their high specific surface area, superlative porosity, and diversity in electronic structure. Herein, a novel porous cobalt-porphyrin-based covalent organic polymer (CoCOP) is fabricated through the Schiff-base condensation reaction, which is used as a difunctional electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The CoCOP possesses a high surface area and strong synergistic effect between the cobalt-porphyrins and the CN groups, resulting in efficient HER and OER performances. The CoCOP required relatively low overpotentials for both HER (121 mV to reach 1.0 mA cm-2 and 310 mV to reach 10 mA cm-2) and OER (166 mV to reach 1.0 mA cm-2 and 350 mV to reach 10 mA cm-2) in alkaline media. This work may provide a new idea for the design of non-noble metal-based coordination polymers with excellent structure and high electrocatalytic performance.

Efficient optical limiting of polypyrrole ternary nanohybrids co-functionalized with peripherally substituted porphyrins and axially coordinated metal-porphyrins.

Herein, three polypyrrole-based nanohybrids were designed and prepared via a nucleophilic substitution reaction, i.e., peripherally substituted porphyrin-functionalized PPy (TPP-PPy), axially coordinated metal-porphyrin-functionalized PPy (SnTPP-PPy), and polypyrrole ternary nanohybrids co-functionalized with peripherally substituted porphyrins and axially coordinated metal-porphyrins (TPP-PPy-SnTPP). The TPP-PPy, SnTPP-PPy and TPP-PPy-SnTPP nanohybrids exhibited improved nonlinear optical and optical limiting performances when compared to the individual PPy and porphyrins under 4 ns, 532 nm laser pulses. Their improved optical nonlinearities were ascribed to a combination of mechanisms and efficient charge transfer effect between the porphyrins and PPy. The charge transfer effect between the porphyrins and PPy was confirmed by UV-vis absorption, fluorescence and electrochemical impedance spectroscopy. The TPP-PPy-SnTPP ternary nanohybrid exhibited the best nonlinear absorption, nonlinear refraction and optical limiting performances because of more effective charge transfer effect, which provides a new avenue for the development of polypyrrole-porphyrin systems in the fields of nonlinear optics and optoelectronic devices.

Graphene-oxide-supported covalent organic polymers based on zinc phthalocyanine for efficient optical limiting and hydrogen evolution.

In this contribution, two constituent-tunable metallophthalocyanine covalent organic polymers (MPc-COPs) covalently attached to graphene oxide (GO-PcP 1 and GO-PcP 2) were rationally designed and fabricated for optoelectronics and electrocatalysis. The resultant GO-PcP nanohybrids exhibit markedly enhanced nonlinear optical and optical limiting performances over those of their components and physical mixtures at 532 nm in the nanosecond pulse range. The optical nonlinearity can be further optimized by tuning the linkage type between the four-branched tetraamine metallophthalocyanine units. The hydrogen evolution reaction (HER) is investigated by linear sweep voltammetry in a 0.5-M H2SO4 aqueous solution. Under optimal conditions, the overpotentials needed to reach 1 mA cm-2 are measured as 237 and 210 mV for GO-PcP 1 and GO-PcP 2, respectively, which places GO-PcP 2 as the best metallophthalocyanine polymer-based HER catalyst to be reported in the literature. The improved performances were ascribed to the positive synergistic effects between MPc-COPs and GO. Notably, the present study introduces a new strategy for the precise preparation of MPc-COP-based nanomaterials while exploring their applications to develop highly efficient optical limiters and electrocatalysts.

Graphene and Carbon-Nanotube Nanohybrids Covalently Functionalized by Porphyrins and Phthalocyanines for Optoelectronic Properties.

In recent years, there has been a rapid growth in studies of the optoelectronic properties of graphene, carbon nanotubes (CNTs), and their derivatives. The chemical functionalization of graphene and CNTs is a key requirement for the development of this field, but it remains a significant challenge. The focus here is on recent advances in constructing nanohybrids of graphene or CNTs covalently linked to porphyrins or phthalocyanines, as well as their application in nonlinear optics. Following a summary of the syntheses of nanohybrids constructed from graphene or CNTs and porphyrins or phthalocyanines, explicit intraconjugate electronic interactions between photoexcited porphyrins/phthalocyanines and graphene/CNTs are introduced classified by energy transfer, electron transfer, and charge transfer, and their optoelectronic applications are also highlighted. The major current challenges for the development of covalently linked nanohybrids of porphyrins or phthalocyanines and carbon nanostructures are also presented.

Polyaniline decorated Bi2MoO6 nanosheets with effective interfacial charge transfer as photocatalysts and optical limiters.

Polyaniline (PANI)-decorated Bi2MoO6 nanosheets (BMO/PANI) were prepared by a facile solvothermal method. Different characterization techniques, including X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, diffuse reflectance ultraviolet-visible spectroscopy, photoluminescence spectroscopy, electrochemical impedance spectroscopy, photocurrent spectroscopy, and nanosecond time-resolved emission studies, have been employed to investigate the structure, optical and electrical properties of the BMO/PANI composites. The wide absorption of the samples in the visible light region makes them suitable for nonlinear transmission and photocatalytic activity studies. The associated photocatalytic activity and optical nonlinearities for the BMO/PANI composites are shown to be dependent on the PANI loadings. The rational mechanisms responsible for deteriorating pollutants and improving optical nonlinearities were also proposed, which could be mainly attributed to the efficient interfacial charge transfer and the interfacial electronic interactions between PANI and Bi2MoO6. The photoluminescence spectroscopy, electrochemical impedance spectroscopy, and photocurrent spectroscopy studies confirmed that the interface charge separation efficiency was greatly improved by coupling Bi2MoO6 with PANI. The tuning of photocatalysis and nonlinear optical behaviors with variation in the content of PANI provides an easy way to attain tunable properties, which are exceedingly required in optoelectronics applications.

Covalent functionalization of reduced graphene oxide with porphyrin by means of diazonium chemistry for nonlinear optical performance.

Reduced graphene oxide (RGO)-porphyrin (TPP) nanohybrids (RGO-TPP 1 and RGO-TPP 2) were prepared by two synthetic routes that involve functionalization of the RGO using diazonium salts. The microscopic structures, morphology, photophysical properties and nonlinear optical performance of the resultant RGO-TPP nanohybrids were investigated. The covalent bonding of the porphyrin-functionalized-RGO nanohybrid materials was confirmed by Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and thermogravimetric analysis. Attachment of the porphyrin units to the surface of the RGO by diazotization significantly improves the solubility and ease of processing of these RGO-based nanohybrid materials. Ultraviolet/visible absorption and steady-state fluorescence studies indicate considerable π-π interactions and effective photo-induced electron and/or energy transfer between the porphyrin moieties and the extended π-system of RGO. The nonlinear optical properties of RGO-TPP 1 and RGO-TPP 2 were investigated by open-aperture Z-scan measurements at 532 nm with both 4 ns and 21 ps laser pulses, the results showing that the chemical nanohybrids exhibit improved nonlinear optical properties compared to those of the benchmark material C60, and the constituent RGO or porphyrins.

Crystal structure of 2-butyl-sulfanyl-4,6-bis-[(E)-styr-yl]pyrimidine.

In the title compound, C24H24N2S, the dihedral angles between the central pyrimidine ring and pendant benzene rings are 18.46 (6) and 5.95 (6)°. The butyl-sulfanyl side chain adopts a twisted conformation [S-C-C-C = 177.34 (10)° and C-C-C-C = 67.68 (18)°]. No directional inter-actions beyond typical van der Waals contacts could be identified in the crystal.

Crystal structure of 2-butyl-sulfanyl-4,6-bis-[(E)-4-(di-methyl-amino)-styr-yl]pyrimidine.

In the title compound, C28H34N4S, the dihedral angles between the pyrimidine ring and the pendant 4-(di-methyl-amino)-benzene rings are 14.20 (5) and 14.56 (4)°. The butyl side chain adopts an anti conformation [C-C-C-C = -171.53 (13)°]. No directional inter-actions beyond van der Waals contacts occur in the crystal structure The title mol-ecule has a D-A-D structure, in which the pyrimidine ring is the electron-withdrawing part and the 4-(di-methyl-amino)-benzene rings are the electron-donating parts.

Allyloxyporphyrin-functionalized multiwalled carbon nanotubes: synthesis by radical polymerization and enhanced optical-limiting properties.

Allyloxyporphyrin-functionalized multiwalled carbon nanotubes (MWCNT-TPP) were synthesized by radical polymerization and characterized by FTIR, UV/Vis absorption, and X-ray photoelectron spectroscopy; elemental analysis; TEM; and thermogravimetric analysis. Z-scan studies revealed that this nanohybrid exhibits enhanced nonlinear optical (NLO) properties compared to a control sample consisting of a covalently unattached physical blend of MWCNTs and porphyrin, as well as to the separate MWCNTs and porphyrin. At the wavelengths used, the mechanism of enhanced optical limiting likely involves reverse saturable absorption, nonlinear scattering, and photoinduced electron/energy transfer between the MWCNTs and the porphyrin. The role of electron/energy transfer in the NLO performance of MWCNT-TPP was investigated by Raman and fluorescence spectroscopy.