The effect of the synergy between vacancy defects and a phosphorus dopant on the hydrogen evolution reaction (HER) of nanocarbon was revealed for the first time both experimentally and theoretically, and the as-prepared catalysts show near-Pt HER activities, which are the best among metal-free catalysts.

Metallophthalocyanines (MPcs) with the especially active metal-N-4 catalytic sites have the great potential for the electrocatalytic CO2-to-CO conversion. However, the masking of metal-N-4 catalytic sites attributed to the strong pi-pi interaction and the difficulty in capturing CO2 severely limits their catalytic efficiency. Herein, we designed a self-supported electrode that tetra-beta-carboxy phthalocyanine cobalt(II) (TcPcCo) was anchored into polyaniline (PANI) chain in isolation using the carbon paper (CP) as a support. The PANI with unique porous structure provides large surface area, rapid electron transfer, and unimpeded pathways for CO2 diffusion. More importantly, sufficient CO2 captured by PANI can continuously spill over to metal-N-4 active sites and be reduced into CO. The synthesized electrode for CO2 reduction reaction (CO2RR) could maintain a high CO Faraday efficiency of over 95% (maximum 99.3%) at an extraordinary wide potential range of 450 mV (from -0.50 V to -0.95 V vs. RHE), ranking foremost among the previously reported phthalocyanine-based electrocatalysts. Furthermore, relative to TcPcCo, the CO turnover frequency (TOF) of PANI-TcPcCo/CP significantly improves, especially at the more negative operating potential (about 7 similar to 68 times). Theoretical calculations further reveal that the introduce of PANI optimizes the free energy barrier of CO2RR intermediate at Co-N-4 site, thus accommodating the*COOH formation, and also suppresses the competition of hydrogen evolution reaction. This work presents a new perspective on advancing the catalytic CO2RR capability of molecular materials by regulating the chemical environment surrounding a catalytically active site.

借助超声辅助复合的方式,制备了四-β-(对硝基苯氧基)酞菁钴/酸化多壁碳纳米管复合材料(TNPPcCo/aMWCNT).采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X-射线光电子能谱仪(XPS)等多种手段对TNPPcCo/aMWCNT进行了表征.结果表明,TNPPcCo独特的周边取代基增强了其与aMWCNT间的π-π作用,促进了两者的复合,从而提高了TNPPcCo/aMWCNT的结构稳定性.电化学传感性能测试结果表明,TNPPcCo/aMWCNT修饰的玻碳电极在检测扑热息痛时,检测限可达0.4μmol·L-1(S/N=3)且选择性较好,这归因于TNPPcCo与aMWCNT间的协同作用.

The successful isolation of metal phthalocyanines into graphene-supported microporous polyanilines results in rich exposure to active sites, rapid electron transfer and efficient gas transport channels, which synergically enhance NH3 sensing.

Although the activity of electrocatalysts towards oxygen evolution reaction (OER) has achieved considerable improvement by modulating the intrinsic electron structure, the role of supports to OER performance, often being reduced to enhancing the conductivity, is not fully explored. In this paper, a proof-of-concept study based on a series of hybrids of nickel iron (hydr)oxide nanoparticles (NiFeO NPs) and carbon supports with different oxidation level compared the motivation of supports for OER activity. The key to implementation lay in anchoring and growing of NiFeO NPs on the various carbon supports by electrostatic assembly and subsequent in-situ reduction. A series of experiments indicated that the strong coupling of metal ions and graphene oxide (GO) contributed to the formation of ultrasmall NiFeO NPs (approximate to 2 nm) and the firm interaction between NiFeO NPs and GO, which in turn resulted in exposing more metal atoms, modulating local electron structure of active sites, and accelerating the charge-transfer ability. The OER activity of optimal NiFeO NPs anchored on rGO (NiFeO NPs/rGO) was significantly elevated, achieving an overpotential as small as 201 mV at 10 mA cm(-2) and a low Tafel slope of 68 mV dec(-1), as well as remarkable stability. Such exciting capacity for catalyzing OER prevailed over the vast majority of previously reported transition-metal electrocatalysts, even superior to numerous noble metal-containing catalysts. The electrolyzer employing NiFeO NPs/rGO and commercial Pt/C for anode and cathode could be powered by a solar cell for efficient alkaline seawater splitting. This work opens up a universal and scalable way for further advancing the intrinsic activity of energy-related materials.

Electrochemical detection of catechol (CC) based on the integrated nanocomposite electrodes with high sensitivity and excellent selectivity is highly desirable for environment monitoring and assessment. In this work, the methylated tetra-β-(N,N-diethylaminoethoxy)phthalocyanine cobalt(II)/electrochemically reduced graphene oxide ((MtPcCo/ErGO)n) multilayer films were successfully constructed via a directly coupled layer-by-layer assembly strategy based on the electrostatic attraction as well as π-π stacking interaction, and consequent in situ electroreduction. The formation of the robust multilayer films only relies on the alternately self-driven combination of the [MtPcCo]4+ and GO but without addition of any polymer or surfactant adhesives. The directly coupled multilayer films can play such roles of coordination as promoting sensitive response signal, regulable layer architecture, oriented transmission of electrons, and electrical conductivity. As a result, the tailored (MtPcCo/ErGO)10 film can work as an efficient electrocatalyst for CC oxidation and sensitive detection. The oxidation current density (j) of CC is widely linear to its concentration from 5 to 150 μm and 150 to 350 μm, respectively, with a low detection limit of 0.53 μm (S/N = 3). Furthermore, the good selectivity, reproducibility and long-term storage stability make the multilayer film suitable for the practical CC determination.

Nanostructure engineering of heteroatom-doped carbon catalysts can greatly enhance their electrocatalytic activity by increasing the accessible active sites and beneficial physical properties (e.g., surface area, conductivity, etc.). Herein, we successfully constructed ultra-thin N,P co-doped carbon (NPC) on the surface of multi-walled carbon nanotubes (CNT) by using phytic acid (PA) as a "guide". The rich phosphate groups in PA allow them to be covalently modified on the surface of CNT by the condensation reaction and to further attract large aniline monomers through acid-base interactions, resulting in the uniform and tight bonding between polyaniline and CNT after the polymerization process. During the subsequent thermal reaction, PA also serves as a self-sacrificial dopant for the formation of ultra-thin NPC and the doping amount of P in NPC can be easily adjusted by changing the amount of PA. Due to the abundance of active sites, large electrochemically active surface area and rapid electron transfer, the developed CNT@NPC presents remarkable electrocatalytic activities for the hydrogen evolution reaction (HER) with an overpotential of 167, 440 and 304 mV to reach a current density of 10 mA cm-2 in acidic, neutral, and alkaline electrolytes, respectively. In particular, its acidic HER activity exceeds that of most reported metal-free electrocatalysts and is comparable to that of some excellent transition metal-based catalysts. The approach proposed here is of potential importance for the preparation of ideal heteroatom-doped carbon/nanocarbon composites for use in a variety of future energy conversion systems.

AbstractEven though transition‐metal phosphides (TMPs) have been developed as promising alternatives to Pt catalyst for the hydrogen evolution reaction (HER), further improvement of their performance requires fine regulation of the TMP sites related to their specific electronic structure. Herein, for the first time, boron (B)‐modulated electrocatalytic characteristics in CoP anchored on the carbon nanotubes (B‐CoP/CNT) with impressive HER activities over a wide pH range are reported. The HER performance surpasses commercial Pt/C in both neutral and alkaline media at large current density (>100 mA cm−2). A combined experimental and theoretical study identified that the B dopant could reform the local electronic configuration and atomic arrangement of bonded Co and adjacent P atoms, enhance the electrons’ delocalization capacity of Co atoms for high electrical conductivity, and optimize the free energy of H adsorption and H2 desorption on the active sites for better HER kinetics.

The doping amount of heteroatoms in N, S co-doped carbon nanotubes (CNT-NS) was accurately and extensively regulated by retarding pyrolysis-gas diffusion. The effect of the content of N and S on the hydrogen evolution activity of CNT-NS was revealed for the first time both experimentally and theoretically.

Modulating the allocation of nitrogen and phosphorus in graphene by a judiciously designed supramolecular architecture achieved a record-low overpotential in nonmetallic doped graphene for the HER.

The development of effective methods for synthesizing and stabilizing ultrafine supported metal catalysts is not only advantageous but significantly recommendable in electrocatalytic water splitting. Herein, carbon nanotube inlaid with ultrasmall FeP nanoparticles is engineered by a controlled in situ catalytic carbon etching strategy. The key for implementing this favorable effect lies in the close self-assembly of iron(II) phthalocyanine onto carbon nanotube by pi-pi stacking interactions. During the pyrolysis process of the assemblies in the air, the generated ultrasmall Fe2O3 nanoparticles stemming from iron(II) phthalocyanine can synchronously in situ catalyze the decomposition of the adjacent carbon nanotube, which makes Fe2O3 nanoparticles tightly anchor onto, and/or even infiltrate into, the carbon nanotube. Subsequently, the inlaid ultrasmall FeP nanoparticles are obtained by a facile anion-exchanging process. Thanks to the more accessible active sites, inlaid structure, and superior electrical conductivity originating from the interconnected carbon nanotube, the as-obtained hybrid exhibits superior electroactivity toward hydrogen evolution reaction, achieving a very low overpotential (68 mV at 10 mA cm(-2)), favorable reaction kinetics, and remarkable stability. The present strategy provides a novel method for strengthening the interactions between ultrasmall catalyst particles and the conductive supports for achieving efficient and robust catalysts toward energy storage and conversion systems.

Energy-saving electrolytic hydrogen production is the precondition for implementing large-scale hydrogen energy exploitation. Replacing the sluggish water oxidation reaction with thermodynamically more favorable pollutant electro-oxidation (degradation) is a very promising approach to combine energy-efficient hydrogen production and sewage treatment. Herein, a homologous asymmetrical two-electrode configuration, made up of self-assembly induced mosslike Fe2O3 and FeP on electro-oxidized carbon paper (ECP), was used to electrolyze the integrated hydrazine oxidation-hydrogen evolution system. The free-standing Fe2O3/ECP electrode was fabricated by pyrolyzing iron phthalocyanine/ECP self-assembly in air and serves as an anodic reaction catalyst. Subsequent phosphidation of the Fe2O3/ECP leads to the formation of the FeP/ECP catalyst for hydrogen evolution reaction. The cross-linked mosslike Fe2O3 and FeP nanoparticles densely covered on the surface of ECP provide richly exposed catalytic sites and the well-distributed stacking holes among nanoparticles offer the expedited electrolyte/gas transmission path. Coupled with hydrazine oxidation, the Fe2O3/ECP parallel to FeP/ECP configuration presents a superior cell voltage of only 0.93 Vat 10 mA cm(-2) for synchronous hydrogen production, which is substantially lower than that of traditional overall water splitting system. Besides the low-voltage-driven energy efficiency, the catalyst electrodes also afford excellent run-to-run reproducibility and stability, as well as good batch-to-batch repeatability. Such a win-win coupling strategy offers the prospect of synchronously achieving energy-saving hydrogen production and the green conversion (or degradation) of hydrazine in wastewater.

The development of effective approaches for preparing large-area, self-standing, ultrathin metal-based nanosheets, which have proved to be favorable for catalytic applications such as water electrolysis, is highly desirable but remains a great challenge. Reported herein is a simple and versatile strategy to synthesize ultrathin Co3 O4 and CoP NSs consisting of close-packed nanoparticles by pyrolyzing cobalt(II) phthalocyanine/graphene oxide (CoPc/GO) assemblies in air and subsequent topotactic phosphidation while preserving the graphene-like morphology. The strong π-π stacking interactions between CoPc and GO, and the inhibiting effect of the tetrapyrrole-derived macrocycle for grain growth during the catalytic carbon gasification contribute to the NSs forming. The resulting homologous Co3 O4 and CoP NSs display outstanding catalytic activity in alkaline media toward the oxygen evolution reaction and the hydrogen evolution reaction, respectively, ascribed to the richly exposed active sites, and the expedited electrolyte/ion transmission path. The integrated asymmetrical two-electrode configuration also presents a superior cell voltage of 1.63 V at 10 mA cm-2 for overall water splitting, accompanied with the excellent durability during long-term cycling. Further evidences validate that this strategy is appropriate to fabricate graphene-like ultrathin NSs of many other metal oxides, such as Fe2 O3 , NiO, MoO3 , and mixed-metal oxides, for various applications.

Manipulating the morphology and protonic acid doping of polyaniline (PANT) is significant for optimizing its NH3-sensing. Herein, tetra-beta-carboxyphthalocyanine cobalt (II) (TcPcCo) acted as the dopant and structure-directing agent simultaneously to fabricate the uniform fibrous network like PANI (PANI-TcPcCo hybrids) by a one-step polymerization at low temperature. During the reaction process, the protonic acid groups in TcPcCo not only induced the aniline monomers polymerizing into one-dimensional nanofibers (consist of both solid and hollow cylinders) with abundant tiny protuberances on the surface but also successfully doped into PANI. The resulting PANI-TcPcCo hybrids displayed the enhancement in terms of the good conductivity, the large gas adsorption capacity, and the unobstructed channels for the electron and gas transport. The central metal atoms of TcPcCo present the strong and selective affinity to NH3. Meanwhile, the deep-seated conversion of PANI's molecular structure after exposure in NH3 could occur due to the presence of TcPcCo. Thus, the PANI-2.5TcPcCo sensor showed the excellent NH3-sensing performance at room temperature, including an ultrahigh and fast response (802.7% and similar to 17.0 s for 100 ppm of NH3), a very low detection limit of 10 ppb (about 5000 parts of human olfaction limit of detection, 55 ppm), and superior NH3-sensing stability and selectivity. The strategy developed here provides a reliable and valid way to synthesize functional PANI-based hybrids with unique morphology and appropriate doping, which are able to be extended to other areas.

The effective integration of carbon nanotubes with polyaniline for the rapid and sensitive detection of NH3 was achieved via a tetra-β-carboxyphthalocyanine cobalt(ii)-mediated non-covalent coupling.

As vital biological mediators, the accurate detection of nitrite (NO2 -) and hydrogen peroxide (H2O2) is desirable for clinical monitoring and diagnosis. Herein, cationic 2,9,16,23-tetra[4-(N-methyl)pyridinyloxy]phthalocyanine cobalt(ii) ([TMPyPcCo]4+) and acid-treated multiwalled carbon nanotubes (aCNTs) were alternately self-assembled on the glassy carbon electrode (GCE) by means of the electrostatic interaction, leading to a 3D loose and interconnected assembly of [TMPyPcCo/aCNTs]n multilayer films. In the [TMPyPcCo/aCNTs]n films, [TMPyPcCo]4+ is anchored onto the surface of aCNTs without any inert polymer binders, which is beneficial to expose more active sites for electrocatalysis. The effective combination of [TMPyPcCo]4+ and aCNTs brings many advantages in electrochemical detection, involving the fast oriented transmission of charges, permeable channels for ion adsorption and transport, and more sensing sites, thus the [TMPyPcCo/aCNTs]n films display excellent electrochemical sensitivity towards both NO2 - and H2O2. The responses of NO2 - and H2O2 vary linearly with respect to the concentration from 5 µM to 30 mM and 10 µM to 9 mM. Furthermore, the superior cycling stability, reproducibility, and selectivity make [TMPyPcCo/aCNTs]n films suitable for the real samples.

Stably dispersed nanohybrids, carbon nanotubes covalently linked with phthalocyanine cobalt(ii), are prepared by applying a simple bridging strategy, which yield superior sensor performance for H2S at room temperature.

4-Nitrophenol (4-NP) sensors with high sensitivity and reproducibility are desirable for biosafety and environmental monitoring. Herein, cationic tetra-beta-(N,N,N-trimethylaminoethoxy) phthalocyanine cobalt(II)/acid-treated carbon nanotubes multilayer films, marked as (tmaePcCo/CNT)(n), films (n represents the bilayer number), were successfully constructed on glassy carbon electrode (GCE) by a facile, effective layer by layer (LBL) electrostatic assembly method without the assistant of polyelectrolyte. Because CNTs within the multilayer films are beneficial to collect and transfer charges, and polyelectrolyte-free assembly ensures active sites exposing, the obtained (tmaePcCo/CNT)(10)/GCE exhibits excellent 4-NP electrocatalytic performance with good reproducibility and acceptable stability, a wide linear calibration range over 3 orders of magnitude of 4-NP concentrations (1 mu M-1.8 mM) and a low detection limit of 0.2 mu M (S/N = 3), and it can be applied to the quantification analysis of 4-NP under optimum conditions. This work shows that the LBL multilayer films fabricated without polyelectrolyte can provide a valid way to improve the sensitivity and reproducibility of 4-NP sensors. (C) 2016 Elsevier B.V. All rights reserved.

The hybrid tetra-β-[3-(dimethylamine)phenoxy] phthalocyanine cobalt(ii)/multiwalled carbon nanotube was designed and synthesized, which can serve as an efficient catalyst for sensitive p-aminophenol detection due to synergistic effects between phthalocyanine and the carbon.

Room temperature operation, high sensitivity, low detection limit, fast response/recovery, and excellent selectivity are desirable for a wide range of NH3-sensing application. In this report, well-dispersed 2,9,16,23-tetrakis(2,2,3,3-tetrafluoropropoxy) metal(II) phthalocyanine/multi-walled carbon nanotube hybrids (TFPMPc/MWCNT, M=Co, Zn, Cu, Pb, Pd, and Ni) were prepared by using a solution self-assembly method based on π–π stacking interactions. The as-prepared TFPMPc/MWCNT hybrids show a sensitivity response/recovery and excellent selectivity for NH3 at room temperature, especially TFPCoPc/MWCNT sensor. The sensitivity of TFPCoPc/MWCNT to 50ppm NH3 is about 26%, and the limit of detection is as low as 60ppb. The enhanced NH3-sensing performance is mainly due to the synergistic effect between TFPMPc and MWCNT, e.g. the stronger adsorption interaction of TFPMPc with NH3, the high electrical conductivity of MWCNT, and the fast charge transfer between TFPMPc and MWCNT. By contrast, the response of various TFPMPc/MWCNT sensors decreases in the order of Co>Zn>Cu>Pb>Pd≈Ni, implying that the central metals play a critical role in the sensitivity of NH3. Such results are further evidenced by the binding energies and charge transfers of MPc-NH3 system calculated by the first-principle density functional theory.