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The design and synthesis of low-cost and efficient bifunctional electrocatalysts for water splitting are critical and challenging. Hereby, a bimetallic phosphide embedded in a N and P co-doped porous carbon (FeCoP2@NPPC) material was synthesized by using sustainable biomass-derived N- and P-containing carbohydrates and non-noble metal salts as precursors. The obtained material exhibits good catalytic activities in hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting. The bimetallic alloy phosphide (FeCoP2) is the active site for electrocatalysis. Theoretical calculation indicates that the sub-layer Fe atoms and top-layer Co atoms in FeCoP2 exhibit a synergistic effect for enhanced electrocatalytic performance. The carbon matrix around the FeCoP2 can prevent the corrosion during the catalytic reactions. The hierarchically porous structure of the FeCoP2@NPPC material can promote the transfer of electrons and electrolyte, and increase the contact area of the active sites and electrolytes. N- and P-containing functionalities improve the wetting and conductivity properties of the porous carbon. Due to the synergistic effects, FeCoP2@NPPC requires a low overpotential of 114 and 150 mV at the current density of 10 mA cm-2 for HER in 0.5 M H2SO4 and 1.0 M KOH, and an overpotential of 236 mV for OER in 1.0 M KOH solution, which are much lower than those of FeP@NPPC and CoP@NPPC. Based on the density functional theory calculation, FeCoP2 yields the smallest Gibbs free energy change of rate-determining step among the samples, which leads to better electrochemical performances. In addition, when FeCoP2@NPPC was used as a bifunctional catalyst in water splitting, the electrolyzer needed a low voltage of 1.60 V to deliver the current density of 10 mA cm-2. Furthermore, this work provides a strategy for preparing sustainable, stable, and highly active electrocatalysts for water splitting.

Herein, strongly coupled Mo2C and Ni nanoparticles with in-situ formed interfaces encapsulated by porous carbon nanofibers (Ni-Mo2C-CNF) have been rationally fabricated via pyrolyzing electrospinning polyvinyl alcohol fibers containing hydrothermally obtained NiMoO4 under Ar atmosphere and applied as high-performance and stable electrocatalyst for HER in alkaline electrolytes. Powered by NiMoO4 as homologous bimetallic precursor, the Ni-Mo2C-CNF possesses numerous in-situ formed Ni-Mo2C interfaces, which facilitates the synergistic effect between Ni and Mo2C, improving the conductivity and thus boosting the electrocatalytic performance towards HER. In the meantime, the porous carbon nanofibers with well encapsulated Ni-Mo2C active components stacks, constituting conductive network, which promotes the mass transport, electron transfer, active sites exposure and electrocatalytic stability. As a result, the Ni-Mo2C-CNF features prominently in HER, as it demands a low overpotential of 196 mV but is able to stably yield the current density of 10 mA cm−2 with a small Tafel plot of 54.7 mV dec−1. The method demonstrated in our work to synthesize bimetallic heterostructured materials will offer valuable inspiration to construct promising non-precious electrocatalysts for diverse vital renewable energy applications.

The SiO2/WO3/NiWO4 composites modified carbon nanofibers (SiWNi-CNFs) were prepared by a facile electrospinning method with following carbonization process under nitrogen atmosphere. The as-obtained SiWNi-CNFs were characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray photoelectron spectra (XPS), X-ray powder diffraction (XRD), FT-IR spectroscopy and Raman spectroscopy. As revealed by the electrochemical measurement, the SiWNi-CNFs prepared with SiW12/NiAc2 molar ratio of 1:1 presented best hydrogen evolution activity with a small Tafel slope (48 mV dec−1) among all the as-prepared samples. Notably, the as-prepared catalysts exhibit a small onset potential (0.29 V vs. reversible hydrogen electrode), high current density and excellent stability. The experimental results pointed that the SiWNi-CNFs processes more efficient hydrogen evolution properties than that other contrast samples. This is due to the SiO2/WO3/NiWO4 composite modified on the surface of carbon nanofibers can generate numerous active sites from the synergistic effect of each component. At the same time, the intimate combination of ternary oxide and carbon nanofibers can accelerate the electron transfer, enhance the stability and hinder the aggregation of active components during the carbonization. Moreover, the net-like structure stacked by carbon nanofibers should render the exposure of active sites and facilitate the mass transport for the HER process.

Rational design of non-precious materials with high-performanced and stable electrocatalytic activity for hydrogen evolution reaction (HER) is vital for the wide application of renewable energy device. In this work, we successfully fabricated a binder-free catalyst comprising Ni and V2O3 grown on Ni foam (NF) via annealing hydrothermally resultant Ni3V2O8/NF in a H2/Ar atmosphere and applied it as a non-precious HER electrocatalyst. The as-fabricated material denoted as Ni@V2O3/NF behaves with a unique structure in form of Ni nanoparticles wrapped by V2O3, which should be attributed to the rolling up of nanosheet caused by the Ni outward diffusion from Ni3V2O8 nanosheet during the pyrolysis process. Moreover, the oxygen vacancies-rich V2O3 can donate electron to the in-situ formed Ni nanoparticles and restrict their overgrowth, which regulate the electronic structure of nanohybrid, facilitate HER kinetic process and create abundant accessible active sites. Hence, the Ni@V2O3/NF demonstrates superior HER activity delivering current density of 10 mA cm−2 at an appropriate overpotenial of 19 mV with a low Tafel slope of 48.5 mV/dec and long-term stability in alkaline solution. This work will provide inspirations to the exploration of Ni-V based electrocatalysts for various emerging energy applications.

Transition/alkaline earth metal oxide composite nanofibers (TAMNs) Ca 3 Co 4 O 9 and MgCo 3 O 5 as a new class of oxide materials for hydrogen evolution were successfully fabricated by electrospinning followed by calcinations under mild condition, and characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), high resolution transmission electron microscope (HR-TEM), Raman spectroscopy, X-ray powder diffraction (XRD) and electrochemical method. The layered Ca 3 Co 4 O 9 and MgCo 3 O 5 nanofibers (NFs) have promising capabilities as electrocatalyst for hydrogen evolution, exhibit low Tafel slope of 76 and 98 mV/decade for hydrogen evolution reaction (HER). The affordability and electrocatalytic properties have endowed TAMNs as a potential replacement for precious metal in electrocatalytic applications.

Ordered mesoporous Cu–Mg–Al composite oxides were synthesized via the one-pot evaporation-induced self-assembly strategy. Using this method, copper was first homogeneously incorporated into the ordered mesoporous spinel matrix. After H2 reduction treatment, according to X-ray diffraction (XRD) and transmission electron microscopy (TEM) results, copper existed as metallic nanoparticles with the size of 6–10 nm that well decorated the parent mesoporous skeleton. The metallic nanoparticles were then re-oxidized to copper oxide when exposed to air or during CO oxidation reaction at low temperatures. Thus, copper migrated from bulk spinel phase to the surface after the reduction–oxidation treatment. Moreover, the copper on the surface was re-incorporated into the bulk spinel phase by further thermal treatment at much higher temperature in the presence of air. The correlation between the state of copper in the mesoporous composite oxides and the catalytic performance toward CO oxidation was studied. It was found that copper existed as oxide nanoparticles on the surface of mesoporous Mg–Al skeleton is much more active than that existed as lattice Cu ions in spinel phase.

Five electrolytes based on Ce0.8Nd0.2O1.9 with or without 1000 ppm SiO2 (NDC and NDCSi) are synthesised via a sol–gel process. Composite electrolytes are prepared by mixing NDC and NDCSi sols with 10 wt% precalcined La0.9Sr0.1Ga0.9Mg0.1O3−δ (LSGM) powders. The structure and ionic conductivity of these compounds are investigated by X-ray diffraction, field-emission scanning electron microscopy, and alternating current impedance spectroscopy. The result indicated that the LSGM additives can significantly promoted the grain boundary conductivity of the composite electrolytes. The total conductivity of the composite electrolytes significantly increased with increasing grain boundary conductivity. This paper thereby proposes LSGM as new scavenger materials able to mitigate the harmful effects of SiO2 impurities on grain boundary conduction in NDCSi. Indeed, these additives substantially increase both the grain boundary and the total conductivity of NDCSi.

Ordered arrays of a TiO2@polyaniline core–shell nanocomposite exhibiting specific capacitance as high as 820 F g−1 at 1 A g−1 were prepared by the combination of hydrothermal and in situ chemical polymerization methods. The specific capacitance retention of the nanocomposite is over 85% after 1000 charge and discharge cycles at a current density of 10 A g−1, suggesting good cycling stability.

The long, uniform and smooth Ni(NO 3 ) 2 -loaded polyvinyl alcohol nanofibers were prepared via electrospinning on a nonconductive quartz plate. The nanofibers were stabilized at 300 °C for 3 h in nitrogen atmosphere, and then the continuous heating to 800 °C at the rate of 2 °C min −1 keeping 3 h was used to prepare nickel-doped carbon nanofibers (Ni:CNFs). The composites were characterized with Raman spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The Ni:CNFs were used as the working electrode to sense paracetamol (PCT) and glucose (GLU), respectively. When sensing PCT, the Ni:CNFs electrode showed an electrochemical behavior like on macroelectrode; but for GLU, it displayed an electrochemical behavior like on microelectrode. For both of the species, higher sensitivities on the Ni:CNFs electrodes were obtained than those on bulk glassy carbon and nickel electrodes.

A-site nonstoichiometric electrolytes (La0.95Sr0.05)xGa0.9Mg0.1O3−δ (LSGM, x = 0.97, 1.00, 1.03), and their composites Ce0.8Nd0.2O1.9 (NDC)–LSGM, were synthesized and investigated. The nonstoichiometry efficiently enhanced the total conductivity of LSGM electrolyte, and the A-site deficient composition showed the highest total conductivity above 550 °C (σt,LSGM(x=0.97) = 0.880 S m−1 > σt,LSGM(x=1.03) = 0.808 S m−1 > σt,LSGM(x=1.00) = 0.582 S m−1 at 600 °C). The cubic fluorite and perovskite structures were adopted by all the composites. The LSGM additive significantly promoted the grain growth of the composite electrolyte. The grain boundary conductivities of the composite electrolytes were more or less 5–10 times higher than that of NDC electrolyte at 500 °C. The optimum A-site nonstoichiometry was found to be x = 0.97 in composite electrolytes. This study provides a possible route to design high performance single phase or composite electrolytes for SOFCs.

A novel porous MOF based on the layer framework and p-sulfonatocalix[4]arene nanocapsule has been established, which is assembled by molecule recognition. The channel structure of compound 1 shows the proton-conductive property with 5.42 × 10−7 S cm−1 at 298 K and 95% relative humidity.

The fabrication of cost-effective hydrogen evolution reaction (HER) catalyst is a critical demand for environment-friendly energy generation with the replacement of precious metal based materials. As a powerful substitute for such purpose, Keggin heteropoly acid (HPA) H3PW12O40 (PW12) was taken as a crucial precursor to form the P–W–Ni oxide nanocomposites via electrospinning method with subsequent calcination. The characterizations of scanning electron microscopy, high resolution transmission electron microscope, x-ray powder diffraction, thermogravimetric analysis, Fourier transform infrared, Raman spectroscopy, and electrochemical method illustrated that the obtained composites were constituted of tungsten oxide phosphate (W18P2O59), nickel tungstate (NiWO4), and tungsten oxide (WO3). The crystalline PW12Ni5O43.5(isogenous) obtained at molar proportion of PW12 to NiAc2 in 1:5 exhibited excellent HER properties with small Tafel slope of 57 mV/decade and low overpotential of −0.35 V. The crystalline PW12Ni5O43.5(isogenous) nanocomposite synthesized from PW12 as precursor holds more excellent HER electrocatalytic performance than that of sample fabricated from (NH4)10W12O41 and H3PO4 as precursors. This is due to the uniformity morphology of PW12Ni5O43.5/FTO (isogenous) and enhanced synergistic effect between oxide components resulted from the favoring electrospinning process with the introduction of PW12. In this paper, PW12Ni5O43.5/FTO (isogenous) ternary nanocomposite were prepared as a facile and simple process, which allows easy control, good reproducibility, and cost-effectiveness. And PW12Ni5O43.5/FTO (isogenous) have excellent HER electrocatalytic performance.

A glassy carbon electrode (GCE) was covalently modified by 4-phosphatephenyl (4-PP). Sensing paracetamol (PCT) via linear sweep voltammetry in sulfuric buffer solution of pH 1.02 at 36.8?degrees C, the 4-PP-modified GCE showed high electrochemical sensitivity and long reusability. PCT-loaded poly(vinyl alcohol) (PVA) nanofibers were prepared by electrospinning. Based on the calibration curve of PCT on the 4-PP-modified GCE, the PCT release process from the nanofibers was electrochemically monitored in real time via two routes. The results showed that the covalently modified GCE can be repeatedly used as real-time electrochemical monitoring platform for drug release from drug-loaded nanofibers in the long term.

Palladium nanoparticles (PdNPs) modified indium tin oxide (ITO) electrode was fabricated via electrospinning followed by calcination. The results of scanning electron microscopy (SEM) images and X-ray photoelectron spectroscopy (XPS) indicated the PdNPs were immobilized on the ITO electrode surface successfully. The electrochemical behavior of the modified electrodes could be adjusted easily by changing the collected time of electrospinning. The prepared electrodes exhibited high sensitivity, good reproducibility and stability toward NO2-. The current responses were linear with NO2- concentrations in a wide range with low detection limit. The proposed method can be successfully applied to the determination of NO2- in real water samples. (C) 2012 Elsevier Ltd. All rights reserved.

Poly(vinyl alcohol) (PVA) nanofiber mats were collected on indium tin oxide (ITO) substrate by electrospinning method. A multilayer film composed of α-[P 2 W 18 O 62 ] 6− (abbr. P 2 W 18 ), a polyoxometallate (POM) anion, and poly(diallymethylammonium chloride) (abbr. PDDA) was fabricated by layer-by-layer (LBL) self-assembly technique on the PVA/ITO electrode. The PDDA/P 2 W 18 multilayer film could be unselectively or selectively deposited on the PVA/ITO electrode via changing the amount of PVA nanofibers on the ITO substrate. The scanning electron microscope (SEM) images showed that when the electrospun time was short the PDDA/P 2 W 18 multilayer film was unselectively deposited on PVA nanofiber mats because the amount of PVA nanofibers was too little to cover most of the ITO substrate. However, when the electrospun time was long enough, the PDDA/P 2 W 18 multilayer film was selectively deposited on PVA nanofiber mats because of the larger surface area and higher surface energy of PVA nanofibers in comparison with the flat ITO substrate. Growth process of the multilayer film was determined by cyclic voltammetry (CV). Electrocatalytic effects of the PDDA/P 2 W 18 multilayer film unselectively and selectively deposited on the PVA/ITO electrode on NO 2 − were observed.

Chitosan is a cationic biopolymer that has many electrochemical applications because of its ability to interact with anionic surface-active molecules. In present experiment, chitosan nanofibers were successfully deposited on indium tin oxide (ITO) substrates by electrospinning chitosan solution. After neutralization with saturated Na2CO3 aqueous solution to maintain its fibrous structure, α-[P2W18O62]6− (abbr. P2W18) was immobilized on the chitosan nanofibers by one step self-assembly technique. The scanning electron microscope (SEM) images showed that P2W18 was mainly deposited on chitosan nanofibers. The cyclic voltammetric responses showed three well redox couples of P2W18. Electrochemical behavior of the electrode prepared under different condition of pH value was investigated. In addition, the modified electrode exhibited high electrocatalytic activity for reduction of NO2-. Keywords: Modified electrode, Electrospinning, Chitosan nanofibers, One step self-assembly, Polyoxometalate, Electrocatalysis

Supramolecular organized multilayers were constructed by multiwalled carbon nanotubes modified with ferrocene-derivatized poly(allylamine) redox polymer and glucose oxidase by electrostatic self-assembly. From the analysis of voltammetric signals and fluorescence results, a linear increment of the coverage of enzyme per bilayer was estimated, which demonstrated that the multilayer is constructed in a spatially ordered manner. The cyclic voltammograms obtained from the indium tin oxide (ITO) electrodes coated by the (Fc-PAH@CNT/GOx)n multilayers revealed that bioelectrocatalytic response is directly correlated to the number of deposited bilayers; that is, the sensitivity is tunable by controlling the number of bilayers associated with ITO electrodes. The incorporation of redox-polymer-functionalized carbon nanotubes (CNT) into enzyme films resulted in a 6-10-fold increase in the glucose electrocatalytic current; the bimolecular rate constant of FADH2 oxidation (wiring efficiency) was increased up to 12-fold. Impedance spectroscopy data have yielded the electron diffusion coefficient (De) of this nanostructure to be over 10(-8) cm2 s(-1), which is typically higher than those systems without CNT by at least a factor of 10, indicating that electron transport in the new supramolecular architecture was enhanced by communication of the redox active site of enzyme, redox polymer, and CNT.

In this paper, the adsorption and refrigerating performances of a composite adsorbent (S40) and its host microporous silica gel matrix (S0) are investigated comparatively in which water is used as refrigerant. The composite adsorbent is developed by impregnating the silica gel (S0) with calcium chloride. A lab-scale single-bed adsorption chiller system, functioning without any valve on its refrigerant circuit, is designed and used as test rig. The mass ratio (MR), defined as the ratio of the specific cooling power (SCP) of S40 to that of S0, is found to be higher than 2, while the COP has been improved by 25%, in average. The S40 has been tested to have, not only the capacity of adsorbing water vapour more than twice as much as the S0 does, but also, kinetically, to adsorb and desorb faster. The cycled amounts of refrigerant (CAR), calculated from measured isobaric adsorption levels, further show that the S40 can be regenerated at lower temperatures, with respect to S0.

Electrospun poly (vinyl alcohol) (PVA) nanofibers mat was collected on indium tin oxide (ITO) substrate. Heat crosslinked nanofibers mat became water-insoluble and firmly fixed on ITO substrate even in water. Oppositely charged poly (allylamine hydrochloride) (PAH) and Dawson-type polyoxometalate (POM), Na6P2Mo18O62 (P2Mo18), were alternately assembled on PVA nanofibers-coated ITO substrate to construct multilayer film through an electrostatic layer-by-layer (LBL) technique. The scanning electron microscope (SEM) images showed that P2Mo18 multilayer film was selectively deposited on PVA nanofibers while the unoccupied space by nanofibers on bare ITO was acted as substrate at the same time because the electrospun nanofibers have larger surface area and surface energy than the flat substrate. The cyclic voltammograms current responses of the P2Mo18 multilayer film on PVA/ITO electrode showed three well-defined redox couples of P2Mo18, but very small because P2Mo18 multilayer film was selectively deposited on PVA nanofibers with poor conductivity. In addition, the photochromic behavior of P2Mo18 multilayer film on PVA/ITO was investigated through UV–vis spectra and electron spin resonance (ESR). Fourier-transform infrared (FT–IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) proved that the charge-transfer complex was formed between PAH and P2Mo18 after UV irradiation. Keywords: Modified electrode, Electrospinning, Nanofibers mat, Polyoxometalate, Layer-by-layer, Photochromic

To elucidate the mechanism of stimuli-responsive permeability and to optimize the design, the nanostructure of polymeric composite membranes, developed in our laboratory, was characterized. The membranes were prepared to contain various amounts of stimuli-responsive nanoparticles of poly(N-isopropylacrylamide-co-methacrylic acid), with or without polyelectrolyte coating. Scanning electron microscopy and X-ray photoelectron spectroscopy were used respectively to examine the morphology and surface chemical composition, whereas atomic force microscopy and laser scanning confocal microscopy were employed to characterize the in situ surface and internal structure of the membranes in aqueous media of various pHs. The porous structure was evidenced in the presence of the nanoparticles. The surface content of the nanoparticles increased with increasing particle concentration while the polyelectrolyte coating was nearly undetectable. AFM images revealed that the particles in the membranes shrank with a concomitant increase in pore size as the buffer pH decreased. LSCM results indicated that particles were distributed through the membrane as interconnected clusters.

MnCo2O4 nanofibers (MCNFs) were successfully synthesized by electrospinning followed by a calcination process under mild conditions. The structural and morphological characterizations of MCNFs were performed by x-ray powder diffraction (XRD), thermogravimetric analysis (TGA), Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical method was used to measure the electrocatalytic hydrogen evolution reaction (HER) properties of MCNFs. Electrochemical studies show that the developed MCNFs possess excellent electroactivity towards HER with low hydrogen-evolution overpotential and a small Tafel slope. In addition, electrospinning can promote the materials into nano-sized architectures with large surface area, which can effectively enhance the electrocatalytic HER properties of MCNFs.

Gold nanoparticles (NPs) of 10–50 nm in diameter were synthesized on nitrogen incorporated diamond-like carbon (DLC∶N) thin film electrode by electrodeposition. The deposition process of Au was investigated by cyclic voltammetry and chronoamperometry. The morphology of Au NPs was characterized by scanned electron microscopy. The potentiostatic current-time transients showed a progressive nucleation of Au and growth controlled by diffusion according to the Scharifker-Hills model. The electrochemical properties of Au-DLC∶N electrode and its ability to sense glucose were investigated by voltammetric and amperometric measurements. The results showed that the Au NPs acted as nanoelectrodes improved the electron transfer and electrocatalytic oxidation of glucose on DLC∶N electrode. The Au-DLC∶N electrode exhibited fast sensing response, a linearity from 0.5 to 25 mM and a detection limit of 120 µm. The stable electrochemical properties of Au-DLC∶N electrode hinted its potential application as a glucose biosensor.

Ordered 2D arrays of ferromagnetic Fe/Co alloy nanoparticle rings with diameters of 2–12 µm were fabricated via plasma etching and subsequent pyrolytic treatment of template directed self-assembled rings of a highly metallized polyferrocenylsilane metallopolymer precursor.

The comparison between two kinds of single-layer reduced graphene oxide (rGO) sheets, obtained by reduction of graphene oxide (GO) with the electrochemical method and hydrazine vapor reduction, referred to as E-rGO and C-rGO, respectively, is systematically studied. Although there is no morphology difference between the E-rGO and C-rGO films adsorbed on solid substrates observed by AFM, the reduction process to obtain the E-rGO and C-rGO films is quite different. In the hydrazine vapor reduction, the nitrogen element is incorporated into the obtained C-rGO film, while no additional element is introduced to the E-rGO film during the electrochemical reduction. Moreover, Raman spectra show that the electrochemical method is more effective than the hydrazine vapor reduction method to reduce the GO films. In addition, E-rGO shows better electrocatalysis towards dopamine than does C-rGO. This study is helpful for researchers to understand these two different reduction methods and choose a suitable one to reduce GO based on their experimental requirements.