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Pt decoration is known to be one of the most promising strategies to enhance the performance of TiO2 hydrogen gas sensors, while the effect of Pt-decorating concentration on the sensing performance of TiO2 and the specific interaction between Pt and TiO2 have not been fully investigated. Here, a series of TiO2 nanoarray thin films with differing amounts of Pt decorated (Pt/TiO2) is fabricated, and the H2-sensing performance is evaluated. A switch in the response from P-type to N-type is observed with increasing Pt decoration. The response additionally depends on the H2 concentration: resistance increases in low H2 concentrations and decreases in hydrogen concentrations higher than 40 ppm. This is explained by the competitive adsorption of hydrogen between the Pt nanoparticles (Pt NPs) and the exposed TiO2 surface. The preference for H2 adsorption and splitting between Pt and TiO2 is established by DFT calculations. Humidity brings preferential adsorption of H2O on the surface of Pt, which affects the following adsorption and splitting of H2, thus resulting in a P-N switch of the sensing performance. The detailed dynamic reaction process is described according to the findings.

Zircon (ZrSiO4) is a distinctive material widely investigated and applied for its superb physicochemical advantages. To date, great challenges remain in the synthesis of high-quality zircon powders for their stringent crystallization requirements at elevated temperature and inherent preferential growth along the [200] direction. Herein we, for the first time, present monodisperse spherical zircon (MSZ) powders synthesized via a facile one-step hydrothermolysis at 200 °C by rationally manipulating the Lewis acid–base complexation of zirconium with competitive ions (Lewis basic R ligands) in a Zr–OH–R–F quaternary system. Systematical investigations were revealed encircling the complexation of Zr4+ with the R ligands from various sources, which involve the adjusting acids (HR), Zr/Si reactants and halogen-containing mineralizers. Sufficient acidity from the adjusting acid and weak enough Zr–R affinity are confirmed as two paramount factors modulating the crystallization and growth of high-quality MSZ crystals, which undergo a unique metamorphic morphological transition from monolayered, to multilayered, to donut-shaped and ultimately to micrometer-sized spherical particles. The hydrothermal zircons are first confirmed as Zr-deficient (Zr/Si ratios

A common issue the high-voltage cathode materials of secondary batteries suffered from is oxidative electrolyte decomposition inducing rapid capacity fading with discharge/charge cycling. Herein, a...

Honeycomb-like nitrogen-doped porous carbon (HNC) is prepared by using poly(2,6-diaminopyridine) as nitrogen-enriched precursor and silica as hard template. After carbonization and template removal, the obtained HNC possesses an interconnected 3D hierarchical porous structure and a nitrogen level up to 15.31 at.%. Owing to the hierarchical porous structure and abundant active sites in the carbon matrix, the HNC exhibits an excellent capacitive performance with a high specific capacitance of 398 F g−1 at a current density of 0.1 A g−1 and exceptional cycling stability (110.4% retention after 5000 cycles). This work provides a facile and efficient strategy for the large-scale production of nitrogen superdoped interconnected hierarchical carbon framework for high performance supercapacitors.

With the increasing usage of hydrogen energy, the requirements for hydrogen detection technology is increasingly crucial. In addition to bringing down the working temperature, further improvement in the response and broadening the detection range of hydrogen sensors in particular are still needed. TiO2 based sensors show great promise due to their stable physical and chemical properties as well as low cost and easy fabrication, but their detection range and low concentration response requires further improvement for practical applications. Here (002) oriented rutile TiO2 thin films are prepared by a hydrothermal method followed by annealing in either air, oxygen, vacuum or H2 and the hydrogen sensing performance are evaluated. Raman results show that TiO2 thin films annealed in vacuum and hydrogen have more oxygen vacancies, while those annealed in air and oxygen have a more stoichiometric surface. Annealing in an oxygen-rich atmosphere is shown to extend the detection range of the TiO2 sensors while annealing in anaerobic atmospheres increases their response. At high hydrogen concentrations surface adsorbed O2− is the dominant factor, while at low concentrations the Schottky barrier between Pt and TiO2 is key to achieving a high response. Here we show controlling the TiO2 surface properties is essential for optimizing hydrogen detection over specific concentration ranges. We demonstrate that adjusting the annealing conditions and ambient provides a simple method for tuning the performance of room temperature operating TiO2 based hydrogen sensors.

Graphene has attracted more attention as advanced electrodes for supercapacitors due to its unique geometry structure and outstanding physicochemical property. But its low specific capacitance, especially low volumetric capacitance, has greatly restricted the practical application of graphene electrode materials. Herein, we synthesized nitrogen-containing graphene networks by using 2, 3-diaminopyridine (O-DAP) as functional agent in a facile hydrothermal route. During the hydrothermal process, not only the pyrrolic-N, but also the pyrazine-N is produced in the graphene lattice at the edge/defect site of graphene because of the double –NH2 in DAP reactant. Owing to the high nitrogen content (17.5 at%), special nitrogen configuration, and high density (1.66 g cm−3), the N-containing graphene networks present high gravimetric capacitances up to 353 F g−1 and high volumetric capacitances over 586 F cm−3 in 1 M H2SO4 electrolyte. More remarkably, the N-containing graphene electrodes exhibit exceptional rate capability with a capacitance retention of 80.6% at a high current density of 20 A g−1 and good cycling stability of 91.5% retention after 5000 cycles in a symmetrical two-electrode configuration.

Core-shell structural Ni(OH)2@MnO2 electrodes with widened potential window and great stability are prepared through a two-step strategy, in which freestanding Ni(OH)2 discs grow on nickel-foam as core and wrinkled MnO2 coatings are electrodeposited as shell. The MnO2 shell successfully inhibits the O2 evolution process at the high oxidation potential so that the potential window of Ni(OH)2@MnO2 electrode is up to 1 V. Besides, the Ni(OH)2@MnO2 electrode presents a high specific capacity of 642.3 C g−1 at 1 mV s−1 and a long cyclic life without capacity fading, which is a breakthrough against the poor stability of reported Ni(OH)2/MnO2 electrodes Remarkably, an asymmetric supercapacitor (ASC) constructed by Ni(OH)2@MnO2 electrode and activated carbon electrode delivers a high energy density of 66.7 Wh kg−1 at a power density of 485.7 W kg−1 under potential window of 1.7 V. Furthermore, the ASC exhibits an energy density of 17.8 Wh kg−1 at a high power density of 14571.4 W kg−1 and a capacitance retention of 101.4% after 15,000 cycles, showing great rate capability and stable cyclic performance.

Safety is the most important concern for hydrogen production, transportation and storage. A hydrogen sensor based on (004) oriented anatase TiO2 thin film is fabricated with high density and specific orientation by introducing a seed layer and an annealing process for the TiO2 thin film. The sensor has a detection limit as low as 1 ppm with a remarkable sensitivity of 17% and fast response and recovery times as short as 5 s and 64 s respectively. Modelling results based on density functional theory indicate that the energy barrier for H2 dissociation on the (004) surface is about 0.458 eV. Both Ti and O atoms at the TiO2 (004) surface take part in the H2 dissociation process. The experimental and theoretical results indicate that surface oxygen has played an important role in hydrogen sensing; lowering the density of surface oxygen vacancies is beneficial in promoting hydrogen sensing.

High–energy density lithium-sulfur (Li-S) batteries suffer from short cycling lifespan, poor rate capability, and low sulfur utilization. Here we report design and synthesis of hierarchical porous g-C3N4/reduced graphene oxide (r-GO) as light-weight sulfur host material for Li-S batteries via a poly-condensation method using silica nanoparticles as hard templates. Microstructure of the g-C3N4/r-GO architecture has been characterized. Electrochemical evaluations indicate that the g-C3N4/r-GO/S composite cathode with 75 wt% of sulfur and moderate macropore density in the host material displays the best Li-storage properties. The reversible capacity reaches 589.6 mAh g−1 after 100 cycles at a current rate of 2 C (3.35 A g−1). Especially the rate capability is excellent. Even at 3.5 C, the reversible capacity can reach 55% of the capacity at 0.2 C. This light-weight g-C3N4/r-GO architecture composed of electrical conductive r-GO layers, polar g-C3N4, and hierarchical pores is a promising sulfur host material for high-performance Li-S batteries.

Nowadays it remains a big challenge to achieve high-rate capability and long-term cycling of metal oxide anodes for secondary batteries, due to large volumetric variation-induced unstable electrolyte–metal oxide interfaces. Here we demonstrate that three-layered Fe3O4/carbon hollow spheres with an electrical conductivity of (9.90 ± 0.14) × 10−2 S cm−1 self-assembled through an aerosol-pyrolysis strategy are very promising architectures to achieve long-term cycling at high current density for lithium-ion batteries. They can maintain a reversible capacity of 383 mA h g−1 after 1000 discharge/charge cycles without apparent capacity fading at a current density of 10 A g−1, which is higher than the theoretical capacity of a commercial graphite anode (372 mA h g−1). The nitrogen-doped carbon outer layer, the large-sized dense Fe3O4/carbon mid-layer and the small-sized Fe3O4/carbon inner layer provide fast electron/Li ion transport channels, a restriction “hoop” and buffer space for volumetric variation simultaneously, which enable a stable electrolyte–sphere interface during discharge/charge cycling. Furthermore, the hierarchical Fe3O4/carbon spheres can be facilely and continuously tuned from solid to porous, and then to a hollow structure. This reasonable design through an interfacial control strategy may open a way to synthesize other metal oxide/carbon porous/hollow spheres for energy-storage applications.

As a competitive candidate for replacing graphene that possesses an appropriate fundamental bandgap, structural stability and tunable electronic properties, the recently synthesized honeycomb arsenene has rekindled much enthusiasm in the area of two-dimensional materials. By using first-principles calculations and acoustic phonon limited deformation potential theory, we identify a compelling two-dimensional electronic material, single-layer AsB, which is a direct-gap semiconductor with a bandgap (Eg) of 1.18 eV, almost the same as that of bulk silicon. The orbital projected band structure and electron density as well as partial density of states demonstrate that the frontier state of the planar atomic structural AsB is sp2 orbital hybridization, which is distinct from that of buckled arsenene monolayers. Layer thickness, stacking order and strain are effective ways to tune the frontier states, and thus the band structure and bandgap of AsB. Moreover, thicker AsB exhibits one-layer localized states in the AB-stacking structure, which is in sharp contrast to other layered materials such as MoS2 and phosphorene. Benefiting from the non-localized pz orbital and larger elastic modulus, the carrier mobility of AsB is in the range of 103–104 cm2 V−1 s−1, which is much higher than that of pristine arsenene and some other analogues. Our work provides an effective way to tailor the electronic properties of 2D arsenene, which may open up new avenues for applying it in future nano-optoelectronics and electronics.

A unique double core-shell structure of Si@PANI@TiO2 nanocomposite is synthesized by a simple in-situ growth method. The two shells of polyaniline (PANI) and TiO2, hand in hand, play a key role to improve the electrochemical performance: First, the flexible properties of polyaniline (PANI) effectively accommodate the volume change of Si during the cycling. Second, the good mechanical feature of TiO2 can maintain the structural integrity and attenuate the volume expansion of Si cores. Finally, both of polyaniline and the lithiated TiO2 enhance the conductivity of Si, which promotes the electrons transport. Resulting in the Si@PANI@TiO2 double core-shell nanocomposite exhibits remarkable synergy in large, reversible lithium storage, delivering a reversible capacity as high as 1027 mAh g−1 after 500 cycles and a superior rate capacity of 640 mAh g−1, at a current of 500 and 4000 mA g−1, respectively. This excellent cycling and high-rate capability can be ascribed to the unique and well-designed double core-shell structure with the synergistic effect between polyaniline (PANI) and TiO2.

Manganese oxides are considered as great pseudo-capacitance materials due to their high theoretical capacitance, but they usually suffer from unstable cycle performance and poor rate capability. To explore whether above problems are associated with crystallinity, electrochemical performances of amorphous and crystalline manganese dioxide are thoroughly investigated. Especially, ex-situ XPS and ICP-OES measurements are carried out to examine whether the amount of intercalated Na+ ions is determined by crystallinity and has influence on cycle performance and rate capability. Meanwhile, relationship between pore size distribution and electrochemical performance of manganese dioxides is discussed. We find that the amorphous manganese dioxide with hierarchical pores presents the best performance in this work, which exhibits a specific capacitance of 405.2 F g−1 at a scan rate of 1 mV s−1 and 391.9 F g−1 at a current density of 0.1 A g−1 in a three-electrode system. Moreover, the amorphous-phase nanoparticle electrode possesses an excellent cycle life with 95.1% retention of its initial capacitance after 5200 cycles and a good rate capability of 75.3% retention at 10 mV s−1, which are superior to that of the crystalline one in this work and lots of reported crystalline MnO2 nano-materials.

To suppress shuttling effect and improve electrochemical performance of the sulfur cathode for lithium-sulfur batteries, core-shell structured MoS2@S spherical cathode has been synthesized through a chemical route using MnCO3 as template. The MoS2 shells consist of MoS2 nanosheets. For comparison, MoS2/S cathode has also been synthesized through melting and diffusion of sulfur to commercial MoS2 powders. The electrochemical performance of the MoS2@S and MoS2/S cathodes have been evaluated using cyclic voltammetry, discharge/charge cycling, electrochemical impedance spectroscopy coupled with impedance fitting. The electrochemical performance of the MoS2@S spherical cathode has been much improved compared with that of MoS2/S. The capacity of the MoS2@S spheres can reach 1185.7 mA h g−1 at 0.2 C and 955.1 mA h g−1 at 1 C with initial-cycle coulombic efficiency of 90%. The capacity fading of each cycle is 0.1% during 200 lithiation/delithiation cycles. The MoS2@S spherical cathode with high cyclic capacity and stability is promising cathode candidate for lithium-sulfur batteries.

A yolk structure of C/SiO2/C and a hollow structure of C/SiO2 composites with porous feature are synthesized by one-step method and two steps method, respectively. When evaluate as an anode material for lithium-ion batteries (LIBs), the C/SiO2/C and C/SiO2 deliver an impressive cycle performance and exhibit an excellent rate capacity. More importantly, attributing to the one-step synthesis method of C/SiO2/C, it possesses interconnected micropore and higher special surface area, which provide a more efficient ionic transportation path and facilitate the diffusion of Li+ between the electrolyte and C/SiO2/C, thus the activation time of SiO2 can be effectively shorten. The capacity achieves the steady value of 1135 mAh g−1 (based on the weight of SiO2 in the electrode material) only by 60 cycles at 50 mA g−1 which is much faster than that of C/SiO2 and delivers a high-rate capacity of 390 mAh g−1 at 1000 mA g−1. Considering the good lithium storage abilities and fast-activated features, the C/SiO2/C composites hold promise in applications in practical LIBs.

An oriented TiO2 thin film-based hydrogen sensor has been demonstrated to have excellent sensing properties at room temperature. The exposed high energy surface offers a low energy barrier for H2 adsorption and dissociation. In this work, rutile TiO2 with {101} and {002} facets exposed was controllably synthesized by adjusting the ethanol content of the hydrothermal solvent. The crystalline structure, morphologies, and H2 sensing performance of the samples varied with the relative ratios of {002} and {101} facets. By increasing the ethanol content, the (002) orientation growth was enhanced and the (101) orientation growth was restrained, the size of the nanorods composing the thin film was reduced and the density of the film was increased. All of the prepared TiO2 nanorod array film-based hydrogen sensors performed very well at room temperature. The TiO2 hydrogen sensor with both {110} and {002} facets exposed gave a faster response, as well as better repeatability and stability than those with only {002}...

The graphene foam (GF) was prepared by reducing graphene oxide (GO) with l -ascorbic acid ( l -AA), followed by freeze-drying. Through changing the initial concentration of GO solution, several GFs with different microstructure could be obtained. The higher the initial concentration of GO, the more obviously the layered stacking of graphene sheet. According to the study, GFs with honeycomb microstructure possessed excellent performance on microwave absorption (MA). When the concentration of GO was 2 mg/ml, the resulting sample GF2 showed the best MA properties. When the thickness of the sample GF2 was 2 mm and the mass content of GF2 in the sample was only 3 wt%, the absolute value of the maximum reflection loss (|RL max |) of GF2 could reach 41.0 dB at 16.2 GHz. And 11 GHz bandwidth of RL less than −5 dB, covering the whole Ku, X and half the Xc band, was achieved by GF2 with the thickness of 3 mm.

LiFePO4/graphene composites have been synthesized by a facile surfactant-assisted self-assembly way. In the LiFePO4/graphene composites, graphene could form an effective conductive network for electric transport. The effects of graphene content on structure and electrochemical performance have been investigated. The results show that all LiFePO4/graphene composites have higher rate capability and longer cycling stability than those of primitive LiFePO4. LiFePO4/graphene (with weight ratio of 94:6) displays the lowest charge transfer resistance among all samples and delivers discharge capacity of 132.6 mAh g−1 at 5 C rate, which is much more improved than that of primitive LiFePO4, i.e., 87.5 mAh g−1. Moreover, the capacity retention of all four LiFePO4/graphene composites are about 80% after 1000 cycles, which is much better than that of primitive LiFePO4, i.e., 49%.

Pyridine-enriched graphene sheets (DAP-RGOs) have been successfully prepared at mild reaction conditions from graphene oxide (GO) and 2, 6-diaminopyridine (DAP). High nitrogen content in DAP-RGOs can be readily achieved in a range of 13.1–17.2% by controlling the feed ratios of reactants. The pyridine moieties grafted on the graphene sheets take place a reversible redox reaction and demonstrate faradaic capacitive behavior. Due to its high density (1.59 g cm−3) and reasonable nitrogen content (14.4%), the as-prepared DAP-RGO sample exhibits both high volumetric and gravimetric capacitances of 504 F cm−3 and 317 F g−1 at current density of 0.1 A g−1 in 1 M H2SO4 electrolyte, respectively. Furthermore, the assembled supercapacitor shows an excellent cycling stability with capacitance retention of 90% after 5000 cycles at 2 A g−1.

In recent years, production of H2 through photocatalytic water splitting has attracted considerable attention in the chemistry and material fields. In this work, TiO2 based heterojunction photocatalyst, which is consisted of rutile nanorods and anatase nanoparticles, is systematically studied by controlling the HCl concentration in hydrothermal process. With the help of loaded Pt, an interesting two-peak feature (“M” shape) is observed in the HCl-dependent H2 production efficiency. The peak values are 54.3 mmol h−1 g−1 and 74.4 mmol h−1 g−1, corresponding to 83.9% and 12% anatase phase, respectively. A detailed analysis based on the microstructure and photoluminescence (PL) spectra indicate that the “M” shape feature is directly linked to the HCl-controlled interface area. Moreover, an unexpected zero interface area is revealed at an intermediate HCl concentration. In terms of homogeneous and heterogeneous nucleations, an interface growth mechanism is proposed to clarify its HCl-sensitive character. This work provides a route to enhance the photocatalytic activity in TiO2 based photocatalyst via increasing the interface area.

CH3NH3PbI3-based perovskite solar cells have achieved great success in the past several years. However, their further large scale application is hindered by the toxicity of the Pb. Here, the existence of a stable perovskite structure with close to optimum optical properties for solar cells with Pb replaced by Bi was shown by theoretical modeling. It was found that the cubic perovskite BiI3 framework is maintained only when the polar organic group of CH3NH3+ is dissociated into neutral CH3NH2 molecule and hydrogen. The band gap of the neutral molecular filled CH3NH2BiI3 perovskite structure gives a value of 1.61 eV, which matches closely the solar spectrum with a maximum possible efficiency of 28.5% close to the Shockley–Queisser limit of 33% for a single stage cell, offering a new and promising lead-free route for perovskite solar cells.

Transition metal dichalcogenides for electrocatalytic water splitting are important in renewable energy research, with studies showing that the edge structure and specific surface area are crucial to their electrocatalytic activity. Herein, the design and construction of yolk–shell nanospheres based on molybdenum diselenide-encapsulated molybdenum oxide are reported. Their structures were characterized using various techniques, which showed that the void space between the interior core and outer shell increased the number of active sites. This yolk–shell structure exhibited enhanced and stable electrocatalytic activity in the hydrogen evolution reaction (HER). The HER current density at −0.5 V vs. the reversible hydrogen electrode was increased by 95% (to −256 mA cm−2) compared to that of traditional flower-like molybdenum diselenide. The overpotential of this yolk–shell structure, which was required to drive a current density of −10 mA cm−2, was 65 mV lower than that of flower-like molybdenum diselenide (286 mV). Furthermore, long-term potential cycling and potentiostatic measurement of this catalyst showed favorable stability and durability of electrocatalytic activity. This yolk–shell structure plays a key role in energy conversion processes central to several renewable energy technologies.

Cobalt-based heterogeneous cocatalysts are important substitutions of noble metal cocatalysts in many important commercial chemical processes, but their efficiency is extremely low on a per metal atom basis, because only the atoms located at surface active-sites participate in the chemical reaction. Thus, cocatalysts with small cluster dispersions are highly desirable to maximize the amount of active-sites and enhance the per atom efficiency. Here, we report the synthesis of sub-nanometer Co3O4 clusters which are anchored to 2D ultrathin TiO2(B) nanosheets, as a cocatalyst for H2 evolution reaction (HER). It was found that the conduction type of Co3O4 clusters turns from P-type to N-type, and the heterojunction band structure between TiO2(B) and Co3O4 clusters changes from type II to type I, when the cluster size is reduced from nanometer scale to the sub-nanometer scale. With a suitable energy band matching between TiO2(B) and sub-nanometer Co3O4 clusters, the electrons generated in TiO2(B) during the photocatalytic process reduce the Co ions into metallic Co atoms, which produce excellent photocatalytic stability and extremely high HER efficiency comparable to that of the noble Pt cocatalyst.

Though TiO2 was famous for good chemical stability, as an ultrathin flaky structure, TiO2 nanosheet also got mired in photo-corrosion. Herein, we explored the inner mechanism of photo-corrosion phenomenon among nanosheet structure, and demonstrated the vital role of high specific surface area and perfect dispersity of nanosheet photo-catalyst in H2 evolution reaction, rather than the heterophase junction of TiO2(B)/λ-Ti3O5. Through exploring four different Conditions, we have confirmed the important modification of highly active metal co-catalyst and surfactant PVP for greatly promoted catalytic efficiency and excellent morphology, efficiency stability. In especial, sole addition of PVP not only stabilized the nanosheet morphology, also tripled the original TiO2(B) efficiency, while TiO2-Au-4h(PVP) displayed the highest QE of 30.9 %, and best stability. This work developed an excellent stable TiO2(B) nanosheet based catalyst, also established a possible strategy to settle photocorrosion for other nanosheet mateials under illuminated applications.

Improving thermoelectric performance of self-powered operation of electronics has been a continuous effort to relieve energy crisis and environmental degradation. In the branches of thermoelectric research, multiscale phonon engineering and proper doping are effective strategies to reduce lattice thermal conductivity and enhance electrical conductivity of bulk materials, respectively, yet great challenge remains in the modulation of transport properties for low-dimensional structures. Here we propose to employ doping of Ga in the single-layer octagon-square nitrogene (OS-N) as an alternative way to increase its thermoelectric efficiency. Our work demonstrates that salient electronic performance can be obtained benefiting from the convergence of valence band as well as non-localized pz orbital state. At the same time, the relatively complexed configuration of doped system shows a much increased impeding of thermal transport, which is about thirty times lower than that of elemental two-dimensional nitrogene monolayer. This pronounced improvement is attributed to the softening of phonon branches, which increase the scattering phase space and structural anharmonicity. Our work illustrates the realization of tailoring electronic and phonon properties in the dimensionality reduced system and provides a road map for potential applying it in fields such as thermal management and thermoelectrics.

Bismuth-based solar cells have exhibited some advantages over lead perovskite solar cells for nontoxicity and superior stability, which are currently two main concerns in the photovoltaic community. As for the perovskite-related compound (CH3NH3)3Bi2I9 applied for solar cells, the conversion efficiency is severely restricted by the unsatisfactory photoactive film quality. Herein we report a novel two-step approach— high-vacuum BiI3 deposition and low-vacuum homogeneous transformation of BiI3 to (CH3NH3)3Bi2I9—for highly compact, pinhole-free, large-grained films, which are characterized with absorption coefficient, trap density of states, and charge diffusion length comparable to those of some lead perovskite analogues. Accordingly, the solar cells have realized a record power conversion of efficiency of 1.64% and also a high external quantum efficiency approaching 60%. Our work demonstrates the potential of (CH3NH3)3Bi2I9 for highly efficient and long-term stable solar cells.

An electrochemical sensor for determination of hydroquinone (HQ) and catechol (CC) was developed using Au nanoparticles (AuNPs) fabricated on reduced graphene oxide/polyimide (PI/RGO) film by electroless deposition. The electrochemical behaviors of HQ and CC at PI/RGO-AuNPs electrode were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under the optimized condition, the current responses at PI/RGO-AuNPs electrode were linear over ranges from 1 to 654 mol/L for HQ and from 2 to 1289 mol/L for CC, with the detection limits of 0.09 and 0.2 mol/L, respectively. The proposed electrode exhibited good reproducibility, stability and selectivity. In addition, the proposed electrode was successfully applied in the determination of HQ and CC in tap water and the Yellow River samples.

Recently, the production of hydrogen through water splitting using titania (TiO 2 ) as photocatalyst has received great attention in the new energy field. In this work, a single one-step hydrothermal method is used to synthesize ultra-thin TiO 2 (B) nano-sheets, anatase TiO 2 , and their composite, using ethylene glycol (EG) and ethanol as the solvent. A new composite nanostructure with anatase TiO 2 quantum dots grown on TiO 2 (B) nano-sheets is obtained at certain ratios between EG and ethanol. Even without the help of co-catalyst, a high photocatalytic efficiency, about 45 times of that of rutile-anatase mixed Degussa P25, is observed in the TiO 2 (B)-anatase composite nanostructure. The outstanding performance can be attributed to its large specific surface area, abundant surface active sites, mixed phase promoted efficient charge separation. Moreover, the properly aligned band structure, with the conduction band level of ultra-thin TiO 2 (B) about 0.6 eV higher than that of the anatase, provides a large driving force for the reduction of water.

Hexagonal and cubic Li0.5TiO2 particles have been fabricated through magnesiothermic reduction of Li2TiO3 particles in a temperature range of 600 to 640 °C. The prolonged reduction time results in lattice transition from hexagonal to cubic structure of Li0.5TiO2. Their microstructures, valance state, chemical composition, as well as electrochemical performance as anode candidates for lithium ion batteries have been characterized and evaluated. The hexagonal Li0.5TiO2 exhibits better electrochemical activity compared with the cubic one. Further, the carbon-coated hexagonal Li0.5TiO2 displays improved electrochemical performance with initial reversible capacity of 176.6 mAh g−1 and excellent cyclic behavior except capacity fading in the initial 10 cycles, which demonstrate a novel anode candidate for long lifetime lithium ion batteries.

In order to improve electrochemical performance of inert SiO2 anode for lithium ion batteries, submicro-sized porous SiO2/C and SiO2/C/graphene spheres with the same SiO2 content (43 wt.%) have been synthesized through a simple suspension nebulization and spray pyrolysis method followed by carbonization, where the components of the spheres are mixed uniformly. The addition of graphene results in mesoporous structure of the SiO2/C/graphene spheres. The electrochemical performances of the porous SiO2/C and SiO2/C/graphene spheres have been evaluated, which indicate that the SiO2/C/graphene spheres exhibits much higher cyclic capacity and stability than SiO2/C with reversible capacity retention of 97% over 100 cycles. The graphene additives display very strong effects in reducing charge transfer resistance and improving structural stability of the porous spheres simultaneously. The mesoporous SiO2/C/graphene spheres are promising anode candidate for high energy-density lithium ion batteries.

AuPd bimetallic composite has been prepared on reduced graphene oxide/polyimide (PI/RGO) film by electrodeposition. The AuPd fabricated on PI/RGO film exhibits good conductivity and excellent catalytic properties. AuPd/PI/RGO electrode shows high activity toward hydrogen peroxide (H2O2) for coupling effect between AuPd and PI/RGO film. Based on high electrochemical activity toward H2O2, an amperometric glucose biosensor has been also described, which was achieved by the immobilization of glucose oxidase (GOx) onto the AuPd/PI/RGO electrode. The proposed biosensor displayed good amperometric response characteristics toward glucose, such as a fast response within 3 s and a wide linear range from 0.024 mM to 4.6 mM. In addition, the biosensor was utilized for the detection of glucose in human blood serum that displayed satisfactory results. The present finding might open up a new avenue in the development of high performance bimetallic materials on appropriate supporting materials for electrochemical sensing. (C) 2017 The Electrochemical Society. All rights reserved.

Effective detection of hydrogen at lowered temperature is highly desirable in promoting safety in using this abundant gas as a clean energy source. Through first-principle calculations in the framework of density functional theory, we find that the high-energy (002) surface for rutile TiO2 is significantly more effective in adsorbing hydrogen atoms through dissociating hydrogen molecules. The pathways for the dissociation of hydrogen molecules and sequential migration of hydrogen atoms are identified through searching along various transitional states. Pathways of low potential barriers indicate promise for hydrogen sensing, even close to room temperature. This has been proven through sensors made of thin films of well-aligned rutile nanorods, wherein the high-energy (002) surface dictates the top surface of the active layer of the sensors.

Cellular glutathione plays critical roles in protecting neuronal cells against dopamine induced oxidative stress and electrophilic cellular damage; inspired by above mentioned properties of glutathione, we used glutathione as a polymerization inhibitor to develop a dopamine biosensor which can be used in alkaline environment. The detection of dopamine in alkaline environment has been challenged by its polymerization for many years, glutathione as a kind of thiol can be used to prevent the polymerization of dopamine in alkaline environment by eliminating the electrophilic quinone molecules needed during the polymerization. In order to enhance the electrochemical performance of electrode, Ag2Se/MoSe2 composite with large exposed surface areas was synthesized, which improved the sensitivity and stability for dopamine detection. The low oxidation peak potential for dopamine, 0.04 V vs. SCE, indicats that glutathione can realize the electrooxidation of dopamine at lower potential in alkaline environment. In this study, by introducing glutathione to inhibit the dopamine polymerization, sensitive and stable detection of dopamine can be achieved at pH 8.5 based on the Ag2Se/MoSe2/GCE. (C) 2016 Elsevier B.V. All rights reserved.

Pillared graphene composite (GP) is prepared by in situ polymerization and subsequent carbonization of graphene oxide (GO) and polyaniline (PANI) precursors. The interlayer spacing of GO layer can reach 1.418 nm with 200% increase compared with the original spacing of 0.706 nm by the intercalation of aniline monomer through π–π conjugate and electrostatic interactions. After carbonization, the graphene composite is reinforced by the intercalated PANI-converted carbon pillars and also has a nitrogen-doped level of ca. 4.49 atom%. Electrochemical characterization studies show that the GP composite exhibits a high reversible capacity of 653 mAh g−1 at a current density of 100 mA g−1 and an excellent rate capability (343 mAh g−1 at a current density of 1 A g−1), which are superior to graphene owing to the unique pillared and the nitrogen-doped structure.

Carbonaceous material is considered as the most promising anode material for potassium ion batteries (KIBs) in the advantages of low price, stable physical/chemical properties, and renewable resources. However, the moderate capacity and sluggish kinetics cast a shadow over its application. Here, we synthesize multiple active sites decorated porous hollow carbon nanospheres (S/N-PHCs) by a one-step large scalable carbonization method with polypyrrole coated polystyrene and low-cost sulfur as precursors. The obtained S/N-PHCs exhibits an amorphous nanocarbon structure with high specific surface area (502.2 m2 g−1) and S, N content of 9.12 and 3.14 at.%, respectively. The porous hollow nanospheres structure promotes the fully utilization of multiple active sites and a capacitive-dominated K+ storage. Consequently, the S/N-PHCs electrode delivers an ultrahigh specific capacity of 460.6 mAh g−1 at a current density of 100 mA g−1 with an initial Coulombic efficiency of 67.7% and excellent rate capability of 228.1 mAh g−1 at 5000 mA g−1. Moreover, a high reversible capacity of 249.7 mAh g−1 can be retained over 1000 cycles at 1000 mA g−1 (83.4% of the initial specific capacity), demonstrating a remarkable cycle stability. This work provides a scalable and environmentally friendly strategy to achieve hierarchical amorphous carbon as superior anode for KIBs.

Investigating the internal factors that affect the initial coulombic efficiency (ICE) of silicon/graphite (Si/G) composites and improving ICE are critical to promote applications of Si/G composites in lithium-ion batteries. Here, four types of Si/G composites are prepared with different specific surface area, Si–G phase interface and charge transfer impedance (Rct) to study the internal factors affecting the ICE of Si/G composites. The experimental results show that the influencing factors on ICE of Si/G composites are not only specific surface area, but also the Si–G phase interface and Rct. During the first lithiation process of Si/G composites, there are some reversible phase (LixSi, LixC) and irreversible phase (Li2O, Li2SiO4 and organolithium) formed, the ICE of Si/G composites is mainly determined by the irreversible phase. The specific surface area, Rct and Si–G phase interface can affect the reaction kinetics of the materials and the ratio of reversible/irreversible phase content, which ultimately affect the ICE of Si/G composites. A smaller specific surface area and well Si–G phase interface with a low Rct will bring a higher ICE of Si/G composites. This report may provide a new idea for the research of ICE of Si/G composites and promote their practical application.

To compete with commercial lithium-ion batteries, light-weight, conductive and polar hosts with high sulfur loading content are required for lithium-sulfur batteries. Herein, light-weight g-C3N4/carbon hybrid cages as sulfur host have been designed and fabricated using NaCl and nanosized manganese compounds (MnO and MnCN2) as templates via a facile and controllable aerosol-pyrolysis route. The porous g-C3N4/carbon shell is designed to facilitate fast electron/Li ion transports and impede lithium polysulfide shuttle simultaneously. The cage cavity created by the NaCl template is designed to enhance sulfur loading content. Electrochemical evaluations demonstrate excellent cyclic capacity and stability of core-shell structured S@g-C3N4/carbon cathode endowed by the versatile structural and chemical advantages of the g-C3N4/carbon host cages. The first-cycle discharge capacities reach 1517 and 1240 mAh g−1 at 0.2 C and 1 C, respectively, demonstrating efficient utilization of the loaded sulfur. The capacity fading rate of each cycle is 0.09% during 400 discharge/charge cycles (from the second cycle) at 1 C. These light-weight, conductive and polar g-C3N4/carbon cages have been demonstrated to be suitable hosts to load sulfur as high-performance cathode for lithium-sulfur batteries.

Hydrogen sensors with high sensitivity, rapid response and low cost are urgently demanded in today’s industry. In this work, we reported our research on the fabrication process and the relevant sensing mechanisms of a TiO2 film based hydrogen sensor which showed an excellent performance at room temperature in air. The sensor, prepared by hydrothermal methods with a seed layer being introduced during the growth of the thin films, exhibited the concentration detection limit as low as 1 ppm and the response time as short as 9 s. Structural analysis revealed that the introduction of the seed layer resulted in a significant improvement in the quality of the TiO2 thin film, which was intimately related to the sensing properties. The dynamical response process was studied and the corresponding sensing mechanisms were analyzed in detail. It was found that, in addition to the generally accepted Schottky barrier mechanism, the adsorption of H2 molecules at (002) surface of the TiO2 thin film played a key role in achieving such a low detection limit and a short response time for the sensor.

Hexagram-like CoS-MoS2 composites were prepared on indium tin oxide (ITO) conductive glasses via cyclic voltammetry electrodeposition using Co(NO3)2 and (NH4)2MoS2 as precursors and tested for application in hydrogen evolution reaction (HER). The structure of CoS-MoS2 composites was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and X-ray photoelectron spectrum (XPS). Electrochemical characterizations indicate that CoS-MoS2 composites exhibit more excellent catalytic activity and stability than MoS2. Compared with pure MoS2, the hexagram-like CoS-MoS2 composites with increased specific surface area improved the density of exposed active sites, and the Co binding S edges in CoS-MoS2 composites promote the number of highly catalytic edge sites and decreased the binding energy △G H. Moreover, the effects of different substrates on the CoS-MoS2 composites were also investigated. Our further understanding of this highly active hydrogen evolution catalyst can facilitate the development of economical electrochemical hydrogen production systems.

We have reported the chemical blending carbonization method to obtain microporous carbon with high surface area for application as electrode materials in supercapacitors. Aliphatic dicarboxylic acids with different methylene numbers (n = 2, 4, 6, and 8) react with phenolic resin (PF) during curing process. Abundant micropores are created in the carbon matrix after the decomposition of grafted or blocked diacids at temperature higher than 400 °C. The specific surface area (SSA) of the carbonized blending system increases with the diacid chain length, but decreases after n > 4 of the chain length. The maximum SSA of the blending system is up to 605.9 m2/g, which increased approximately 68% compared to that of the neat carbonized PF. Electrochemical investigation indicates that the highest specific capacitances of the blending system reaches 175 F/g at a specific current of 0.1 A/g in 30 wt% KOH aqueous electrolyte. Furthermore, the capacitance maintenance achieves 82.8% as the current density enlarged 55 times.

Three-dimensional grapheme-doped carbon cryogels (CCs) with high specific surface area have been prepared via the self-assembly of graphene oxide (GO) sheets and resorcinol (R)-formaldehyde (F) monomers. The porosity of the composite CCs can be regulated from high mesoporosity to microporosity by adjusting the mass ratio of GO sheets to RF monomers. When the loading amount of GO sheets is 1.3 wt.% in the precursor mixture, the specific surface area of the resulting composite CCs is up to 1178 m2 g−1, which is much higher than that of the neat RF CCs (766 m2 g−1). Furthermore, the as-prepared composite CC electrode displays a high specific capacitance (205 F g−1 at 1.0 mV s−1) and superior rate capability compared to the neat RF CCs.

Taking the geological conditions of a typical coal mine as an example, a fuzzy comprehensive estimation model is developed for judgment of mine water and sand inrush caused by underground mining. According to the geological prototype, three basic conditions of water and sand inrush disaster induced by mining under thin bedrock and thick loose aquifer are revealed. Using analytic hierarchy process (AHP) to determine the weights of evaluation index factors, nine evaluation factors are chosen, and then the degree of membership of evaluation factors is determined through qualitative and quantitative two ways. The dangers of water and sand inrush in the study area are quantitatively analyzed. The risks are divided into four ranks, through calculating, the hazard level of water and sand inrush disaster in study area is 3, it is high risk. The fuzzy system is efficient and easy to use, and the evaluation results are in good accordance with the reality, and provide the decision basis for the safety production of the coal mine.

Here, we report a nano-sized red phosphorous/biomass-derived porous carbon (P@BDPC) which is employed as anode materials for lithium ion batteries (LIBs) via a facile vaporization−condensation−conversion strategy (VCC) with tobacco stem as the carbon precursor. The biomass-derived porous carbon not only acts as the host of red phosphorus to enhance the electrical conductivity, but also minimizes the volume expansion (≈400%) during cycling. The obtained P@BDPC composite with a high red phosphorus content (62.1 wt%) delivers a high specific capacity of 1689 mA h g−1 at 500 mA g−1 with an initial Coulombic efficiency (ICE) of 91.7% and superior rate capability of 599 mA h g−1 at 30 A g−1. Furthermore, a high reversible capacity of 918 mA h g−1 can be retained over 600 cycles at 5 A g−1, indicating a remarkable cycle stability. More importantly, the introduction of agriculture waste-tobacco stem contributes to building low-cost, high-performance anode materials.

Designing an efficient and stable electrocatalyst is key for the enhanced oxygen evolution reaction. This paper proposes a hydrothermal method for synthesising Sn-doped CoOx(OH)2(1-x) (CoOx(OH)2(1-x)-Sn(Ⅳ)). During the preparation process, the morphology of the precursor was controlled by an anionic surfactant. The precursor of the layered structure was mainly formed through the bonding of anionic group SO3H− in SDBS with metal cation Co2+, and the surface area and reaction sites of the precursor were clearly increased. Finally, CoOx(OH)2(1-x)-Sn(Ⅳ) urchin-like spheres were hydrothermally synthesised. The current density of the CoOx(OH)2(1-x)-Sn(Ⅳ) obtained at a potential of 1.95 V was 124.8 mA cm−2, i.e. 2.8 times higher than that of the precursor (44.9 mA cm−2). The Tafel slope of the precursor was 156.1 mV dec−1, i.e. 3.3 times that of CoOx(OH)2(1-x)-Sn(Ⅳ) (48.0 mV dec−1).

Hydrogen production and in-situ storage from water splitting is an attractive technology for clean energy. Here (0 0 2) oriented rutile TiO2 thin films are prepared by the hydrothermal method for photocatalytic water splitting. The H2O molecule efficiently dissociates on the high energy rutile (0 0 2) surface and the highest hydrogen production rate of 28.4 mmol h−1 g−1 is achieved in the film with the lowest density, at a rate comparable to powder TiO2 photocatalysts. The produced hydrogen is stored in-situ in the films with the help of the atomic hydrogen concentration difference between the surface and in the crystal lattice. Theoretical calculations show that water is dissociated on the rutile (0 0 2) surface with a negligible energy barrier. Hydrogen atoms diffused into the sublayers are confined in the TiO2 lattice owing to a high energy barrier for them to overcome to escape from the rutile (1 1 0) surface. The theoretical storage capacity is up to 1.2%, at room temperature and atmospheric pressure, demonstrating the potential for practical room-temperature hydrogen production and storage.

To obtain high-performance sulfur cathode for lithium-sulfur (Li-S) battery, porous graphitized carbon spheres with N doping have been fabricated via an in situ Fe catalysis as sulfur host. The in situ generated Fe nanoparticles play double roles as graphitization catalyst and pore template. The electrical conductivity of the graphitized sample (5.6 S cm−1) is about one order of magnitude higher than that of the amorphous carbon sample (0.63 S cm−1). Correspondingly, the pomegranate-like S@N-doped graphitized carbon cathode displays very good electrochemical performance. A capacity of 600 mAh g−1 is obtained after 150 charge/discharge cycles at a current density of 1 C with a sulfur content of 73 wt%. The pomegranate-like S@N-doped graphitized carbon is promising cathode candidate for high-performance Li-S battery.

Hydrogen sensors combining wide detection range and high response, that can operate at room temperature, are urgently demanded for monitoring different concentrations of hydrogen on a single device. Here, a novel one-step hydrothermal method is reported to construct Nb doped rutile/anatase TiO2 heterophase junctions for a highly sensitive H2 sensor. The Nb concentration in the solvent plays an important role for the heterophase juncton self-assemble, and the reaction time determines the surface morphology giving either a rutile TiO2 nanorod decorated anatase form, or a Nb doped rutile/anatase TiO2 bi-layer structure. An inverse dependence of the detectivity on H2 concentration is obtained as theoretically predicted but previously not experimentally verified for the high concentration region at low temperatures. The H2 concentration detection range is remarkably expanded, extending from 1 ppm to 12000 ppm for nanorod decorated film. The H2 response at 1 ppm is significantly enhanced to 22.5%, and reaches 98.9% in 8000 ppm H2 for the bilayer structure. The remarkablely extended detection range is the result of the massive accumulation of reactive pre-absorbed O 2 − on the surface due to the Nb doping, and the significantly enhanced response at room temperature results from the joint contributions of pre-absorbed O 2 − , film compactness and the heterophase junction. Moreover, Nb doped rutile/anatase TiO2 heterophase juncton films show high stability and humidity resistance for hydrogen sensing.

Preparing conductive composite bipolar plates for fuel cells by compression molding is a promising research direction. The very key point is how to choose the conductivity filler and binder to meet the requirement. In this article, natural graphite and expanded graphite were used as the filler, and phenolic resin and epoxy resin were used as the binder. The composite bipolar plates were prepared by solution intercalation mixing, compression molding, and curing. The variations in electrical conductivity and mechanical properties were evaluated with the resin content. The results show that the types of fillers and binders have significant effects on the performance of composite bipolar plates, and that the thermal stability of all composite bipolar plates is very good at the fuel-cell working temperature. The corrosion current densities were 2, which indicates that the composites developed in this work meet many attributes of bipolar plates for use in polymer electrolyte membrane fuel cells.