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Understanding the phase regulation mechanism of BaTiO3 synthesized by a hydrothermal method is a complicated and challenging task. Here, we successfully prepared cubic and tetragonal BaTiO3 single nanocrystals by changing the ratio of water and ethanol in the solvent. We confirm that the BaTiO3 phase is mainly affected by the hydroxylation process due to the reaction with solvent. In particular, ethanol can be catalytically oxidized by titanium atoms, cause BaTiO3 hydroxylation and promote the formation of a cubic phase. In the mixed solution of ethanol and water, the hydroxylation process is suppressed, which facilitates the formation of the tetragonal phase. The relationship framework between the solvent ratio, phase structure and hydroxyl defects of BaTiO3 is established. Tetragonal BaTiO3 with fewer hydroxyl defects can promote charge transfer and surface reaction after polarization, thereby enhancing their photoelectric catalytic performance. This work provides references for the controllable synthesis of ferroelectric nanocrystals by hydrothermal methods and new insight for the utilization of polarization in photoelectrocatalysis applications.

Construction of heterostructured electrocatalyst with interface effect is an effective strategy for enhancing the alkaline hydrogen evolution efficiency, whereas this process often requires complex treatments. Herein, we proposed a one-step electrodeposition method to obtain heterostructured CoNi-LDH@NiCo alloy on Ni foam (NF) through a competition reduction between NO3− group and metal cations in the electrolyte. The HER performance for the CoNi-LDH@NiCo alloy achieved the current density of 10 mA cm−2 at overpotential of 69 mV in 1 M KOH solution, improved 60% for η10 by comparing with the pristine NiCo alloy. Utilizing the specialized adsorption of CoNi-LDH for H2O and the featured attractiveness of NiCo alloy for H atom, the interface effect of the heterostructure electrocatalyst accelerated the dissociation of water molecules and elevated the catalytic kinetics dramatically. This work points out a potential approach towards the easy construction of inexpensive heterostructured electrocatalysts for HER activity in alkaline medium.

Industrial parks have a very important impact on regional economic development, but the extremely complex and relatively concentrated volatile organic compound (VOC) emissions from industrial parks also result in it being difficult to control VOCs. In this study, we took a large integrated industrial park in the upper reaches of the Yangtze River as an example, conducted a 1-year monitoring campaign of ambient air VOCs, and established a speciated VOC emission inventory based on the measured chemical profiles of the key industries. The comprehensive control index (CCI) of 125 VOCs was evaluated using the entropy weighting method based on comprehensive consideration of three aspects, namely, emission behavior, environmental effects, and health risks of VOCs, to identify priority VOC species and their key sources for VOC control in industrial parks. The total estimated VOC emissions in the industrial park in 2019 were 6446.96 t. Steel production, sewage treatment, natural gas chemical industry, pharmaceuticals, and industrial boilers were the main sources of VOC emissions. In terms of VOC components, halocarbons, aromatics, and OVOCs were the largest groups of VOCs emitted from the industrial park, accounting for 73.75 % of the total VOC emissions. Using the entropy weighting method, we evaluated the index weights of five parameters: emissions, ozone formation potential, secondary organic aerosol formation potential, hazard quotient, and lifetime cancer risk. Based on the CCI, five control levels for VOC species were further established. The VOC species in Level I and Level II, which contain species such as naphthalene, 2-chlorotoluene, benzene, acrolein, and chloroform, should be considered as extremely important priority control species. These results serve as a reference for the development of precise control strategies for VOCs in industrial parks.

The combination of transition metal-based cocatalysts with semiconductors is a promising route to improve the photoelectrochemical performance in solar water splitting. However, it is difficult to evaluate the catalytic ability for cocatalysts quantitatively. Herein, we use kelvin probe force microscopy technique, combining with Mott-Schottky method, to investigate the cocatalysts from the point of surface potential and Femi level. Through synthesis the nickel/cobalt oxide nanoparticles and nanoporous bismuth vanadate (BiVO4), the result indicates the surface potential of NiCoO2 coated BiVO4 is lower than pristine BiVO4 and BiVO4 coated by NiO and CoO cocatalysts respectively. The lower surface potential means a more upward band bending structure at the interface of electrode and electrolyte, which can promote the separation of electron-hole pairs and enhance the charge transfer kinetics. Thus, the NiCoO2/BiVO4 photoanode achieve a remarkable photocurrent density of 2.34 mA/cm2 for water oxidation, and the charge separation and oxidation kinetics efficiencies are 61.9% and 72.7% respectively. In all, our studies provide a new mechanistic insight into cocatalysts for solar energy conversion.

Octahedral CuWO4 microstructurals were successfully obtained via a simple self-assembly solvothermal synthesis pathway for the first time. The effect of organic solvents on the morphology of copper tungstate (CuWO4) was systematically investigated here. In addition, some other parameters, such as the reaction time, sodium salts and a possible mechanism for the formation of CuWO4 with varied morphologies were discussed. We succeed in fabricating and characterizing an octahedral CuWO4 and the results demonstrate that the amount of ethylene glycol (EG) and Cl− plays a critical effect on the formation of unique morphology of CuWO4. According to our investigation, samples obtained show better photocatalytic activity toward the degradation of RhB. Our research provides some new perspective of the morphology control of CuWO4 and is conducive to understand the relationship between the morphology of other wolframite-type microcrystals and their properties.

We have successfully developed a MOF-based (Co3[Fe(CN)6]2·10H2O) strategy to synthesize Co-Fe mixed metal oxide (Co3O4/Fe2O3) nanocubes (denoted as CFNC). The obtained CFNC is applied as both anode and cathode for high-performance symmetric supercapacitors, exhibiting high energy density of 35.15 W h kg−1 at a power density of 1125 W kg−1 as well as excellent stability. Meanwhile, when CFNC is used as electrocatalyst for oxygen evolution reaction (OER), it requires a low overpotential of 310 mV to achieve a current density of 10 mA cm−2 and exhibited excellent stability.

Suitable semiconductor and its efficient coupling with catalysts is vital to hydrogen evolution reaction (HER). Herein, Ternary heterostructured MoS2/Ag/p-type silicon nanowires (SiNWs) array photocathode are constructed by a simple two-step method, where Ag is self-reduced on SiNWs via Galvanic Displacement method and MoS2 is subsequently loaded by direct thermal decomposition. Ag interfacial layer is introduced between Si and MoS2 to facilitate the charge transfer and suppress the recombination of photo-generated electron-hole pairs. MoS2/Ag/SiNWs exhibits an onset potential of 62 mV and photocurrent density of 50 mA cm−2 at −1.0 VRHE, as well as good stability. Besides, MoS2/Ag/SiNWs is capable of generating 325.9 μL hydrogen per minute. The superior HER catalytic activity of MoS2/Ag/SiNWs is contributed to the improved charge transport at the solid–solid interfaces by virtue of Ag layer, allowing more electrons flow from SiNWs to MoS2 and thus effectively separating the photoelectrons and holes. This work demonstrates the potential of novel heterostructure for robust and efficient photoelectrochemical HER.

Pseudocapacitors are promising energy storage devices combining the merit of fast charging ability and high energy density. Constructing electrode materials for pseudocapacitors with two-dimensional (2D) materials has become a trending topic. However, it is still a challenge to address the restacking propensity of the 2D materials and to broaden the operational potential window of pseudocapacitors. We herein demonstrate a facile hydrothermal reaction of synthesizing a three-dimensional V2O3 tubes (assembled with ultrathin nanosheets) coated with MoS2 nanosheets and explore their electrochemical properties for pseudocapacitors. The V2O3 tubes prevent the restacking of MoS2 nanosheets and serve as conductive scaffold for fast electron transport. Owing to the multi-valence of both Mo and V, the potential window of composite is able to straddle between negative and positive potentials. Therefore, the V2O3@MoS2 composite electrode exhibits a broad operational potential range between −1.0 V and +1.0 V, and a high reversible capacitance of 655 F g−1 at 20 mV s−1. Moreover, an asymmetric pseudocapacitor with our composite as a positive electrode achieves a high specific capacitance (108.7 F g−1 at 0.5 A g−1), high energy density (31.8 W h kg-1) and excellent cycling stability (no capacitance decay after 35000 cycles).

In this work, hollow CoS nanobox (noted as HCSN) have been successfully synthesized via annealing and hydrothermal process from zeolitic imidazolate framework (ZIF-67) template. When tested as positive electrode materials in alkaline aqueous electrolyte, it shows high specific capacitance of 720 F g−1 at a current density of 1 A g−1, good rate capability (82.1%) and good cycling stability with 86.4% capacitance retention over 10,000 cycles at 10 A g−1. To further demonstrate the advantages of our ZIF-67 derived materials, asymmetric energy storage device was assembled (HCSN//NC), where the as-prepared HCSN was employed as the anode and ZIF-67-derived nanoporous carbon (noted as NC) as the cathode. This device achieves high energy density (80 Wh kg−1 at a specific power density of 882 W kg−1), good rate capability (53.3 Wh kg−1 even at a specific power density of 7.9 kW kg−1) and long-term stability up to 10,000 cycles. More importantly, it could simultaneously light up 12 LEDs in parallel, demonstrating its potential in practical applications.

Bimetallic nickel–cobalt (Ni-Co) alloy has been regarded as an emerging class of material for the electrochemical hydrogen evolution reaction (HER). However, it operates at an overpotential significantly above the thermodynamic requirement. Here we present a facile one-step electrochemical reduction approach to incorporate fcc NiCo alloy with ⅥB group transition metals (M−NiCo, M = chromium (Cr), molybdenum (Mo), or tungsten (W)). This method enables to control the induction time of protrusion growth (τ) to produce hierarchical structure by imposing high current density (-0.6 A cm−2) and strong electric field on the cathode. Herein, W-NiCo holey nanotower arrays show tremendously enhanced HER activity compared with pristine NiCo alloy, which provides an overpotential of 109.2 mV (reduced by 58.7%) to achieve a current density of −10 mA cm−2, with a Tafel slope of 110.3 mV dec-1 in alkaline medium. The same law applies to the acid electrolyte with an overpotential of 78.5 mV (reduced by 66.1%) and low Tafel slop of 56.6 mV dec-1. Based on the experimental and theory analysis, We find W-doping can promote more active sites exposed, tune the electron configuration, moderate the gibbs free energy of the H intermediate, and accelerate the desorption of H2. It makes the rate-determining step change from Volmer to Heyrovsky reaction and finally surmount the limit of sluggish dynamics. The novel route provides an efficient doping control on Ni-based hierarchical alloys via 4f-orbital electronic and geometric structure engineering, which suggests an environmentally friendly method for energy-related process in practical applications.

The direct Z-scheme heterojunction structure benefits separation and migration of photoinduced carriers while maintaining original redox ability of each component. Nowadays, most Z-scheme structures are fabricated by g-C3N4 with other narrow band photocatalysts due to its low conduction band (CB). In this paper, SiC, another kind of photoelectric semiconductor with low CB, was employed to prepare direct Z-scheme photocatalyst with 2D WO3 by simple water oxidation precipitation method. The component and interface band structure of Z-scheme heterojunction WO3/SiC (WS) were verified by XPS, KPFM, Mott-Schottky method. The photodegradation efficiency and rate constant values of WS-1 for degrading RhB enhanced 2.5 and 5.3 times respectively compared with pristine WO3. Radical capture experiments and ESR tests affirmed that WS-1 photocatalyst produced •OH and •O2－active species, which further confirmed the photogenerated carriers were transmitted through the Z-scheme mode in principle. Band structure investigation showed that the direct Z-scheme structure assembled by WO3 with high valence band (VB) and SiC with low CB could maintain the high photocatalytic activity of active species. Therefore, this study offers a feasible method for construction of a novel and efficient direct Z-scheme photocatalyst.

Spontaneous polarization field in ferroelectric can improve the oxidation kinetics and photocurrent of a photoanode in photoelectrochemical water splitting. But the impact of ferroelectric polarization field on the migration of different charge carriers which have different mobility and diffusion length is still unknown. In this work, we synthesized tetragonal BaTiO3 nanoparticles by solvothermal method successfully and fabricated the hybrid photoanode composed by monoclinic WO3 and BaTiO3 for solar water oxidation. Density functional theory calculations showed that the mobility of electron was faster than that of the hole in WO3, and had a longer diffusion length. We demonstrated that the polarization field of ferroelectric had a greatly impact upon holes migration compared with electrons, thus the thin hybrid photoanode after poling by bias presented a significant improvement of photocurrent (210.5%) under the back-side illumination, and a remarkable augment of charge separation efficiency (94%) and oxidation kinetics (69%) at 1.23 V. Our work provided a deeper understanding of how ferroelectric polarization field affected the photoelectrochemical water oxidation and a general pathway towards enhancing minority carrier collection in photoanode.

Monoclinic bismuth vanadate (BiVO 4 ) has been widely applied as a promising n-type semiconductor for photoelectrochemical (PEC) water splitting because of its low cost, environmentally friendly, and relatively narrow band gap of ∼2.4 eV. Here, we developed a facile fabrication of Mo doped BiVO 4 photoanode on the fluorine-doped tin oxide substrate by electrodeposition method and used these samples to better understand the doping effect for charge separation and charge oxidation kinetics. Compared with the undoped BiVO 4 photoanode, the optimized Mo doped BiVO 4 (3AMo:BV) produced a much higher photocurrent of 1.91 mA/cm 2 at 1.23 V vs. RHE under AM 1.5G illumination for water oxidation. The results of the photoelectric conversion kinetics for various samples revealed that the charge separation and oxidation kinetics efficiencies for 3AMo:BV sample are 74.42% and 49.25% at 1.23 V vs. RHE, while the values for undoped BiVO 4 are 48.04% and 32.98%, respectively. The improved PEC performance for Mo doped BiVO 4 is mainly ascribed to the crystal deformation caused by larger tetrahedral ionic VO 4 and higher photovoltage generated by the interface of photoanode and electrolyte.

Architecturally assembling primary building blocks into the expected geometric heterostructure is a tremendous challenge due to the interfaces dislocation and stretch resulting from the lattice-mismatch between heterogeneous building blocks. Although different dimensional nanomaterials have been synthesized, the branched acanthosphere-like hierarchical architecture is needed to be developed and the growth mechanism should be investigated. Here we design and fabricate an acanthosphere-like NiCo 2 O 4 @α-MnO 2 heterostructures architecture by an “in situ growth” technique of two-steps hydrothermal method. The as-prepared acanthosphere-like NiCo 2 O 4 @α-MnO 2 microspheres (denoted as AM-NCM) have a diameter of 5 ∼ 7 um with a highly open and interstitial three dimensional (3D) architecture formed by α-MnO 2 ultrathin nanosheets leading to faster ion diffusion and improved charge transfer kinetics. Therefore, the hybrid electrodes exhibits exceptional specific capacitances of 695 F g −1 (2.17 F cm −2 ) at the current densities of 3.2 A g −1 (10 mA cm −2 ) and good cycling electrochemical stability with only 2.4% capacitance loss after 1000 cycles and still maintains 92% of its initial value after 6000 cycles. The outstanding performance of the branched AM-NCM reveals its potential to be a promising material for energy storage, and also inspires continued research on the formation of branched hierarchical architecture as energy storage materials.

Lithium ion capacitors (LICs) are considered to be high-performance energy storage devices that have stimulated intense attention to bridge the gap between lithium ion battery and supercapacitor. Currently, the major challenge for LICs has been to improve the energy density without sacrificing the high rate of power output performance. Herein, we designed a three-dimensional (3D) hierarchical porous nanostructure of hydrogen-treated TiO2 nanoparticles wrapped conducting polymer polypyrrole (PPy) framework with single-walled carbon nanotubes (SWCNTs) hybrid (denoted as, H-TiO2/PPy/SWCNTs) anode material for LICs through a conventional and green approach. Such a unique network can offer continuous electron transport and reduce the diffusion length of lithium ions. A greatly lithium storage specific capacity is achieved with reversible discharge capacity ∼213 mA h g−1 (based on the mass of TiO2) over 50 cycles (@ 0.1 A g−1), which is almostly three times compared with raw TiO2 (a commercial TiO2 nanoparticles powder). In addition, coupled with commercial activated carbon (AC) cathode, the fully assembled H-TiO2/PPy/SWCNTs//AC LICs delivers a maximum energy and power densities of 31.3 Wh kg−1 and 4 kW kg−1, a reasonably good cycling stability (∼77.8% retention after 3000 cycles) within the voltage range of 1.0–3.0 V.

Electrocatalysts play a vital role to overcome the slow kinetics of the oxygen evolution reaction (OER). Herein, we developed iron-doped (Fe-doped) NiCoO 2 nanoplates with NaCl-type structure as an efficient electrocatalyst to speed up OER. NiCoO 2 nanoplates doping with different concentration of Fe were optimized. Specifically, the catalytic properties of 10 mol% Fe-doped NiCoO 2 (denoted as FNC0.1) showed outstanding OER catalytic activity, with an overpotential of 302 mV and a low Tafel slope of 42 mV dec −1 at 10 mA cm −2 in 0.1 M KOH. More importantly, the activity of FNC0.1 was only about 3% loss after 10 h of stability measurements at 1.53 V vs. RHE. The dramatically enhanced OER performance of the FNC0.1 might derive from the synergistic interplay of Co, Ni and Fe, a certain level of amorphization and easily hydroxylation after doping Fe. This work demonstrated that doping Fe would be beneficial to improve the OER activities and the stabilities of the catalysts.

Liquid-phase exfoliation is an effective method to fabricate thin nanosheet materials with layered structure. In this paper, we successfully synthesized NH 4 Co 0.4 Ni 0.6 PO 4 ·H 2 O nanosheets with the thickness of about tens of nanometers through liquid-phase exfoliation under ultrasonication. Specifically, the formamide solution was chosen as the exfoliation solvent due to it is capable of entering the interlayer of bulk materials and rapidly swelling between layers. Electrochemistry tests revealed that the optimized exfoliation time was 4 days. The asymmetric battery type energy storage device AC//NH 4 Co 0.4 Ni 0.6 PO 4 ·H 2 O nanosheets showed an energy density of 10.8 Wh kg −1 at the power density of 703.1 W kg −1 . More importantly, the long-term cycle stability measurements demonstrated that NH 4 Co 0.4 Ni 0.6 PO 4 ·H 2 O nanosheets after exfoliation had an ultra-long cycling life that still retained 102.3% of specific capacitance even 10000 continuous charge/discharge cycles.

Monoclinic bismuth vanadate (BiVO4) is a promising semiconductor for photoelectrochemical water splitting. Here, we developed a facile fabrication of BiVO4 double layer photoanode on the fluorine-doped tin oxide substrate by electrodeposition. The BiVO4 double layer photoanode is composed by a dense BiVO4 film as the inner layer and a nanoporous BiVO4 film as the outer layer. Compared to the BiVO4 single layer photoanode, the optimized BiVO4 double layer photoanode produced a much higher photocurrent of 1.15 mA/cm2 at 0.6 V vs. Ag/AgCl under AM 1.5G (100 mW/cm2) illumination. The results of the photoelectric conversion kinetics for different samples revealed that the charge separation and oxidation kinetics efficiencies for the BiVO4 double layer are 47.2% and 51.6% at 0.6 V vs. Ag/AgCl, while the values for BiVO4 single layer are 32.3% and 35.8%, respectively. The improved photoelectrochemical performance for BiVO4 double layer is mainly ascribed to the decrease of defect state at the interface after inserting a dense BiVO4 as an inner layer to prevent the recombination of photogenerated electron-hole pairs.

The surface roughness, weight of phosphating film and wettability of magnesium alloy substrates after abrasion and phosphating treatment were investigated in this work. The interfacial bonding and corrosion properties of a magnesium-based fibre metal laminate (MgFML) were analysed. The results showed that the wettability of the magnesium alloy was greatly influenced by the surface roughness, and the rough surface possessed a larger surface energy and better wettability. The surface energy and wettability of the magnesium alloy were significantly improved by the phosphating treatment. After phosphating for 5 min, a phosphating film with a double-layer structure was formed on the magnesium substrate, and the weight of the phosphating film and the surface energy reached their maximum values. The surface energies of the phosphated substrate after abrasion with #120 and #3000 grit abrasive papers were 84.31 mJ/m 2 and 83.65 mJ/m 2 , respectively. The wettability of the phosphated magnesium was significantly better than the abraded magnesium. The phosphated AZ31B sheet had a better corrosion resistance than the abraded AZ31B sheet within short times. The corrosion resistance of the magnesium alloy was greatly increased by being composited with glass fibre/epoxy prepregs.

Amorphous nanomaterials have been regarded as extremely promising electrode materials for battery-like energy storage device (BESD) due to their atomic disorder, homogeneous and metastable properties, etc. Here, an amorphous NiCo layered double hydroxide (NiCo LDH) with different morphologies is synthesized for the first time by a green, economical and practicable ultrahigh voltage electrophoretic deposition method (EPD), constructing a 3D architecture with high specific surface area as the positive electrode for energy storage. The obtained amorphous NiCo LDH nanosheets/CFP electrode exhibits a high specific capacitance of 347 mF cm −3 and a good retention of 88.3% after 10000 cycles. Moreover, an asymmetric BESD based on the amorphous NiCo LDH/CFP and commercial activated carbon (AC) offers an energy density of 41.67 W h cm −3 at the power density of 0.5 kW cm −3 and excellent cycle life (only 0.3% deterioration of its initial specific capacitance after 10000 cycles). The good performance of amorphous NiCo LDH nanosheets in capacitance is ascribed to the high inner charge storage and efficient ion transportation. This research provides a new method to control the morphologies of amorphous nanomaterials by EPD technique in the future.

CuWO 4 films with feature particle sizes of 100–200 nm and thickness up to 700–900 nm on fluorine-doped tin oxide (FTO) substrates were prepared by hydrothermal synthesis. The prepared CuWO 4 films were treated in hydrogen atmosphere at constant temperature 300 °C for different annealing time and used for photoelectrochemical (PEC) water oxidation. Compared with pristine CuWO 4 film, the optimized hydrogen-treated CuWO 4 film presented three times enhanced photocurrent density of 0.75 mA/cm 2 at 1.2 V vs. Ag/AgCl in 0.1 M Na 2 SO 4 solution under the illumination. The donor density of hydrogenated CuWO 4 film determined by Mott–Schottky analysis was improved one order of magnitude as well. The enhanced photoelectrochemical activity could be attributed to the formation of oxygen vacancies after hydrogen treatment, which facilitated the charge transport and collection.

Previous work demonstrates that Fe2O3 is a promising negative electrode material. Its biochemical performance is strongly influenced by the morphology. Hence, Fe2O3 with nanoparticles, nanosheets and nanorods morphologies are synthesized by hydrothermal method respectively. The relationship between morphology and electrochemical property, particularly in terms of specific capacitance and rate capability are investigated. Detail cyclic voltammetry analysis reveals that the relative contributions of surface capacitive and inner intercalation capacitance change with the morphology. Different contribution of surface relative to inner charge storage leads to different specific capacitance and rate capability. Additionally, Fe2O3 nanosheets delivers a remarkable specific capacitance of 279.9 F g−1 (419.8 mF cm−2) at the scan rate of 5 mV s−1 ascribing to the inner intercalation effect. Moreover, electrochemical tests in neutral and alkaline solution show that the capacitive behavior of Fe2O3 is closely related to the potential window and different electrolyte leads to different contribution of surface relative to inner charge storage. These studies should be useful for elucidating the mechanism and morphological effects on charge storage for Fe2O3-based electrode and provide a direction to enhance its capacitance.

A self-assembled MoSe2 nanolayers/reduced graphene oxide (MoSe2/rGO) foam was prepared using a hydrothermal method. The samples were systematically investigated by X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and high-resolution transmission electron microscopy. Electrochemical performances were evaluated in two-electrode cells versus metallic lithium. It is demonstrated that the obtained MoSe2/rGO nanocomposites show three-dimensional architecture and excellent electrochemical performance as anode materials for Li-ion batteries. The specific capacity of MoSe2/rGO anode can reach up to 650 mAh g−1 at a current rate of 0.1C in the voltage range 0.01–3.0 V (vs. Li/Li+), which is higher than the theoretical capacity of MoSe2 (422 mAh g−1). Additionally, the fabricated half cells have shown good rate capability and long cycling stability with 10.9% capacity loss after 600 cycles under a current density of 0.5C. The excellent performance of the synthesized MoSe2/rGO is attributed to its unique nanostructure, including nanolayered MoSe2, highly conductive rGO networks and mechanically stable 3D architecture.

Dimensionality and rational design of electrode architectures play a crucial role in determining materials' fundamental properties and the electrochemical performance of supercapacitor. For a proof-of-concept, Ni–Co layered double hydroxides (LDH), NiCo2O4 and NiCo2S4 nanosheets supported on carbon fiber paper (CFP) substrate are prepared by simple hydrothermal methods in this work. When tested as the pseudo-capacitor positive electrode, the self-support nanosheets on CFP demonstrate good performance and rate capability as well as excellent cycling life, which contributes to the unique hierarchical nanosheets structure supported on 3D conductive CFP substrate with open permeable channels, facilitating electrolyte penetration and ensuring more efficient ion diffusion and faster electron transport. The asymmetric supercapacitor based on pseudocapacitance of both electrodes is further first realized by using NiCo2S4 nanosheets and FeOOH nanorods as positive and negative materials, respectively. The obtained device can deliver a maximum power density of 8.6 kW kg−1 and energy density of 45.9 Wh kg−1 and even after 10000 reversible cycles at a cell voltage of 1.6 V in aqueous electrolyte, there still retained 86.4% of its initial capacitance.

The reaction mechanism of CO oxidation catalyzed by several Pt3M (M = Pt, Ni, Mo, Ru, Pd, Rh) clusters has been investigated with density functional theory calculations in the present work. The reaction prefers to proceed via Langmuir–Hinshelwood mechanism. The calculated barriers for the reactions mediated by bimetallic clusters are comparable with that catalyzed by monometallic Pt4 cluster. According to thermodynamics and kinetics results, CO oxidation can take place readily without thermal activation and the O2 scission to form OCOO* is the rate-determining-step. Pt3Mo exhibits superior catalytic activity for CO oxidation among all those investigated clusters and good adsorption for O2. The different performance of those bimetallic clusters for CO oxidation is scrutinized with aid of molecular orbital and natural bond orbital population analysis.

A density functional theory (DFT) based method in conjunction with the projector augmented wave and pseudopotential methods have been applied to investigate the adsorption of Pt4 and Pt3Ni on the anatase TiO2 (1 0 1) surface. Two stable Pt3Ni adsorptions with considerable adsorption energies on the anatase TiO2 (1 0 1) surface were identified. Analysis of the partial density (PDOS) of states and Bader charge suggest that the electronic structure of Pt is modified by Ni due to the electron transfer from Ni to Pt atoms in the Pt3Ni clusters. The 2cO (3cO)-PtNi-5cTi conformation of the adsorbed Pt3Ni on the anatase TiO2 (1 0 1) surface provides a more feasible model for electron injection through the Pt3Ni/TiO2 interface. The reactivity of Pt3Ni/TiO2 is superior to Pt4/TiO2 and effectively manifests itself in the eased decomposition of O H bonds derived by methanol and alleviative CO adsorption.

Density functional theory based calculations have been employed to investigate structures and properties of coupled tetragonal pyramid (CTP) Pt 7 based Pt (7 − x ) Ni x ( x = 1, 2, 3) bimetallic clusters, and the reaction mechanism of methanol dehydrogenation to CO on Pt 7 and PtNi bimetallic clusters. The models chosen to catalyze the methanol are Pt 7 (CTP, quintet) cluster and Pt 5 Ni 2 (I) cluster (two Pt atoms in the bottom of Pt 7 (CTP) are replaced by Ni atoms) which is the most stable structure among all the isomers of Pt (7 − x ) Ni x ( x = 1, 2, 3). The methanol dehydrogenation on Pt 7 (CTP) cluster preferentially proceeds along the pathway of CH 3 OH → CH 2 OH → CH 2 O → CHO → CO, while on Pt 5 Ni 2 (І) the pathway of CH 3 OH → CH 3 O → CH 2 O → CHO → CO is more favorable. In addition, the complete dehydrogenation product of methanol, CO, can more easily dissociate from Pt 5 Ni 2 (I) than that on Pt 7 . Electronic configuration analysis shows that charge transfer from Ni to Pt and results in increase of the electron density in Pt 5d orbitals. Moreover, the density of states (DOS) at Fermi level of clusters reduces gradually as the increase of the doped Ni atoms and this improves the catalytic activity for methanol decomposition.

CoNiO nanowire arrays loaded on TiO2 nanotubes (CoNiO/TiO2NTs) are synthesized by a hydrothermal method and used firstly as an anode material for lithium-ion batteries. The morphology, structure and composition of the composite are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The EDS patterns display the atomic ratio of Co to Ni is 0.41:0.59 with accuracy of more than 99%. SEM images show that the diameters of these nanowires range from 10 to 40 nm and the average length approximately 1 μm. Electrochemical characterizations are performed in a three-electrode system to determine the capacity, cyclic stability and to investigate the reaction mechanism. As an anode material for lithium-ion batteries, the CoNiO/TiO2NTs nanocomposite delivers a high areal capacity of 362 μAh cm−2 (1097 mAh g−1, 0.33 mg cm−2) after 40 discharge/charge cycles at a current density of 0.2 mA cm−2 (about 606 mA g−1). EIS results show that addition of Ni to the CoO could increase the conductivity of the composite significantly and improve the kinetic behavior during discharge–charge process. The present finding provides a kind of nanostructure fabrication that might be applied in supercapacitor and solar cells, etc.

3D SnO2 nanoflowers on Ti foil have been synthesized by a simple hydrothermal method without using any surfactant or catalyst. The synthesized 3D SnO2 nanostructures are characterized by X-ray diffraction, field emission scanning electron microscopy and X-ray photoelectron spectroscopy. The FESEM results showed that the nanoflower consists of multiple nanopetals of width ∼5 nm and each SnO2 nanoflower is ∼3 μm in diameter. The time-dependent morphology evolution of SnO2 nanoflowers was studied in detail, and a possible growth mechanism was proposed. In addition, high dispersed Ni nanoparticles was loaded on SnO2 nanoflowers applied in supercapacitor. The electrochemical properties of the 3D Ni/SnO2 nanoflowers were investigated by a series of electrochemical tests.

In this paper, we report the fabrication and characterization of PPy sensitized ZnO nanorod arrays (PPy/ZnO NRs), and its use as a photo-electrode for efficient photo-electrochemical splitting of water under solar light. PPy/ZnO NRs were synthesized on a large scale on indium tin oxide (ITO) by a simple two-step method. UV–vis spectrum showed that PPy/ZnO NRs had strong absorption in nearly the visible light spectrum. FTIR results indicated that there might be a strong interaction between PPy and ZnO with the valence bond of C3O3Zn. The photo-electrochemical measurements of PPy/ZnO NRs exhibited extreme optimal photocurrent up to 0.68 mA/cm2. The results implied that PPy/ZnO NRs offerred improved light absorption, increased photocurrent generation due to the effective charge separation in PPy and ZnO NRs, and enhanced oxidized H2O kinetics because of the synergistic effect of PPy and ZnO NRs.

Highly ordered TiO 2 nanotube arrays (TiO 2 NTs) evenly modified by Ni–Cu nanoparticles were successfully prepared by potential step method. Their morphologies, structures, and alloy composition were characterized by FESEM, XRD and EDS, respectively. The as-prepared Ni–Cu/TiO 2 NTs electrodes were employed for non-enzymatic glucose detection in alkaline electrolyte and showed better electro-catalytic activity compared with Ni/TiO 2 NTs and Cu/TiO 2 NTs electrodes. Factors that affected the electrocatalysis of the electrodes were examined and optimized. Consequently, a sensitive amperometric electrode of glucose was achieved under 0.6 V vs. Ag/AgCl with a high sensitivity (1590.9 μA mM −1 cm −2 ), low detection limit (5 μM) and wide linear range from 10 μM to 3.2 mM ( R 2 = 0.993). Furthermore, the oxidable species such as ascorbic acid and uric acid showed no significant interference in determination of glucose. The experiment results revealed a very good reproducibility and high stability for the proposed Ni–Cu/TiO 2 NTs electrodes.

SnO2@carbon-doping TiO2 nanotube arrays (SnO2@C-TiO2NTs) were synthesized by hydrothermal method and evaluated for lithium ion insertion and photoelectrochemical activity. The composite electrode prepared for 5 h as anode materials for lithium-ion batteries exhibited much improved electrochemical performance due to the aligned pore structure and the synergistic effect of the electrode. A capacity of 142 μA h cm−2 can be obtained after 50 discharge/charge cycles at a high current density of 200 μA cm−2. Moreover, UV–vis results of the sample showed stronger absorption intensity in the range of 200–800 nm compared with bare TiO2NTs. The composite electrode displayed the maximum photocurrent density of 1.80 mA cm−2. This is attributed to the heterojunction formed at the interface between SnO2 and TiO2NTs resulting the enhance charge separation efficiency. Eletrochemical impendence spectroscopy (EIS) also shows that SnO2@C-TiO2 NTs has a noticeably lower charge-transfer resistance.

To develop anode catalysts for photo-assisted direct methanol fuel cell (PDMFC), carbon-doped TiO2 nanotube arrays-supported PtNi alloy nanoparticles with different Pt/Ni atomic ratio (PtNi/C-TiO2NTs) prepared by pulsed electrodeposition method are evaluated as catalysts for photo-assisted methanol oxidation. The cyclic voltammetry (CV) and chronoamperometry results show that the PtNi/C-TiO2NTs prepared at tonPt:tonNi: = 10:7 (ton is the current-on time) with a Pt:Ni atomic ratio of 6.1:5.7 presents the highest catalytic activity for methanol oxidation both in the dark and under illumination. In addition, according to the results obtained from the CO stripping voltammetry and electrochemical impedance spectroscopy (EIS) tests, it was found that the light play an accelerative role in the oxidation of methanol on PtNi/C-TiO2NTs under illumination. The effect of illumination which enhancing the catalytic activity of PtNi/C-TiO2NTs are attributed to (1) methanol and the intermediates be oxidized directly on C-TiO2NTs for the light-induced catalytic effect; (2) more abundant oxygen-donating species be produced on C-TiO2NTs in the presence of light; (3) less COads adsorbing on catalysts due to the presence of stronger metal–support interactions between PtNi alloy nanoparticles and C-TiO2NTs under illumination.

Zn nanoparticles with different size and distribution were loaded on/into TiO 2 nanotube arrays (Zn/TiO 2 NTs) via pulsed electrodeposition method. The morphology of Zn/TiO 2 NTs was studied by field emission scanning electron microscopy (FESEM). The morphology influence of Zn nanoparticles on the photoelectrochemical properties of Zn/TiO 2 NTs were investigated by UV–vis diffuse reflectance spectrum (UV–vis DRS) and photoelectrochemical measurements. The results showed that Zn/TiO 2 NTs composites with an average size at 40–50 nm and uniformly distributed of Zn nanoparticles possessed the narrowest band gap, the best photocurrent response, the highest charge carriers density and minimum charge-transfer resistance. These discrepancies in photoelectrochemical properties of different Zn/TiO 2 NTs samples can be ascribed to the size and distribution effect (morphology effect) of Zn nanoparticles which can influence the transfer and separation of photo-induced carriers generated by TiO 2 NTs.

Ni nanoparticles were loaded on TiO2 nanotube arrays (Ni/TiO2NTs) via pulsed electrodeposition method and employed as catalyst for methanol oxidation in alkaline media. The as-prepared Ni/TiO2NTs catalyst was characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical analyzer. The electrochemical studies showed that Ni/TiO2NTs under illumination exhibited higher catalytic activity and stronger poisoning-tolerance for methanol oxidation than that in the dark. The effect of illumination which improved catalytic activity of Ni/TiO2NTs were attributed to the p–n junction formed at the interface between Ni(OH)2 and TiO2NTs resulting in the photo-generated holes flow into Ni(OH)2, thus, the transmitted holes boosted the oxidation of Ni(OH)2 and produced the OH to oxidize methanol and intermediates that absorbed on the catalyst. The present study shows Ni/TiO2NTs can act as a promising candidate for the anode catalyst in photo assist direct methanol fuel cells (PDMFCs) application.

Evenly dispersed Pt–Ni nanoparticles were loaded on TiO 2 nanotube arrays (TiO 2 NTs) via pulse electrodeposition method and subsequently characterized by FESEM, EDX and XRD. The electrochemical studies showed that the catalytic activities of Pt–Ni/TiO 2 NTs are better than that of Pt/TiO 2 NTs for methanol electro-oxidation in alkaline media both in the dark and under illumination. In addition, due to the interaction of electro-catalysis and photo-catalysis, the catalytic activities of TiO 2 NTs-based catalysts were improved largely under illumination. Base on the results obtained in this work, Pt–Ni/TiO 2 NTs may be used to develop a base for photo assist direct methanol fuel cell.

To predict the outbreak time of algal blooms and its duration in an actual body of water, this paper developed a directed complex networks (CNs) model of algal blooms. This new model was based on the characteristics of CNs theory and the primary factors that influenced algal blooms. By calculating the shortest path and proposing a key degree node model, the role of each influencing factor during algal blooms was evaluated. Based on years of on-site monitoring data (collected from 1992 to 2000) concerning the Han River, a statistical characteristic function G that reflected the relationship between the statistical characteristics of dominant algae blooming and the degree of algal blooms pollution was proposed. The results indicate that the proposed function G is capable of effectively and semi-quantitatively characterizing the outbreak time and the duration of algal blooms. If the value of G in a body of water is less than 32.6, the body of water will outbreak an algal bloom. An increasingly smaller of G value indicates a greater degree of algal blooms pollution and longer bloom duration.

In this paper, highly ordered titania nanotube (TNT) arrays fabricated by anodization were annealed at different temperatures in CO to create different concentrations of surface defects. The samples were characterized by SEM, XRD and XPS. The results showed different concentrations of Ti3+ defects were doped in TNT arrays successfully. Furthermore, after co-immobilized with horseradish peroxidase (HRP) and thionine chloride (Th), TNT arrays was employed as a biosensor to detect hydrogen peroxide (H2O2) using an amperometric method. Cyclic voltammetry results and UV–Vis absorption spectra presented that with an increase of Ti3+ defects concentration, the electron transfer rate and enzyme adsorption amount of TNT arrays were improved largely, which could be ascribed to the creation of hydroxyl groups on TNT surface due to dissociative adsorption of water by Ti3+ defects. Annealing in CO at 500 °C appeared to be the most favorable condition to achieve desirable nanotube array structure and surface defects density (0.27%), thus the TNT arrays showed the largest adsorption amount of enzyme (9.16 μg/cm2), faster electron transfer rate (1.34 × 10−3 cm/s) and the best response sensitivity (88.5 μA/mM l−1).

The failure behavior of an elastic-perfectly plastic body with a crack loaded by two pairs of concentrated shear forces is discussed. The analytical solutions of an eccentric crack in a finite plate loaded by two pairs of point shear forces are obtained. It includes the unit normal vector of the elastic–plastic boundary near the crack line, the elastic–plastic stress fields near crack line and the law of the plastic zone along the crack line with external loads. The solutions of this paper are sufficiently precise near the crack line in elastic-perfectly plastic materials. Subsequently, the present results are compared with solutions based on the minimum strain energy density theory and elastic–plastic solutions under small scale yielding condition. On the basis of the minimum strain energy density (SED) theory, the minimum values of SED in the vicinity of the crack tip are determined, the initial growth orientation of crack are determined. It is found that the normalized load under large scale yielding condition is higher than those under small scale yielding condition when the length of the plastic zone is the same.

In this paper, highly-ordered TiO 2 nanotube (TNT) electrodes fabricated by anodization at 20 V in 0.1 M F − -based solution were annealed in O 2 , N 2 and CO respectively. The surface properties of the TiO 2 electrodes after annealing treatment by different gases were studied by means of photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties of the TNT electrodes were investigated by cyclic voltammetry, steady-state polarization and photocurrent response measurements. The results showed that Ti n+ (n = 0–3) cations and oxygen vacancies existed in the TNT electrode after annealing in CO, leading to a very efficient electron transfer rate of 1.34 × 10 − 3 cm/s. Steady-state polarization measurement and photocurrent response demonstrated that the electrode potential of oxygen evolution reaction (OER) reduced by 20% and the photocurrent response increased by 50% for CO-annealed TNT electrode compared with O 2 -annealed TNT electrode.

Anatase titania nanotube arrays were fabricated by means of anodization of Ti foil and annealed at 400 °C in respective CO and N2 gases for 3 h. Electrochemical impendence spectroscopy study showed that CO annealed arrays possessed a noticeably lower charge-transfer resistance as compared with arrays annealed in N2 gas under otherwise the same conditions. TiO2 nanotube arrays annealed in CO possessed much improved lithium ion intercalation capacity and rate capability than N2 annealed samples. At a high charge/discharge current density of 320 mA g−1, the initial discharge capacity in CO annealed arrays was found to be as high as 223 mAh g−1, 30% higher than N2 annealed arrays, ∼164 mAh g−1. After 50 charge/discharge cycles, the discharge capacity in CO annealed arrays remained at ∼179 mAh g−1. The improved intercalation capacity and rate capability could be attributed to the presence of surface defects like Ti–C species and Ti3+ groups with oxygen vacancies, which not only improved the charge-transfer conductivity of the arrays but also possibly promoted phase transition.

The near crack line analysis method is used to investigate an eccentric crack loaded by shear forces in a finite width plate, and the analytical solution is obtained in this paper. The solution includes: the unit normal vector of the elastic–plastic boundary near the crack line, the elastic–plastic stress fields near crack line, variations of the length of the plastic zone along the crack line with an external loads, and the bearing capacity of a finite plate with a centric crack loaded by shear stress in the far field. The results obtained in this paper are sufficiently precise near the crack line because the assumptions of small scale yielding theory have not been made and no other assumptions have been taken. Subsequently, the present results are compared with the traditional line elastic fracture mechanical solutions and elastoplastic near field solutions under small scale yielding condition. On the basis of the minimum strain energy density (SED) theory, the minimum values of SED in the vicinity of the crack tip are determined, the initial growth orientation of crack are determined. It is found that the normalized load under large scale yielding condition is higher than those under small scale yielding condition when the length of the plastic zone is the same.

By means of numerical simulation, the special phenomenon of zonal disintegration of surrounding rock mass around the diversion tunnels of Jinping II Hydropower Station is analyzed in this paper. In order to model the growth and coalescence of cracks within rock mass in Jinping II Hydropower Station, the weak-element is adopted. When cracks coalesce, failure of deep crack-weakened rock masses occurs and fractured zone is formed. The present result is different from the one obtained by the traditional elasto-plastic theory. The numerical results show that the slip-line zonal fracture is created within rock mass around the diversion tunnels in Jinping II Hydropower Station. Meanwhile, the magnitude and distributions of fractured zones are determined by numerical simulation. It is shown that the present results are in good agreement with the one observed by model tests. Through sensitivity analysis, the effects of stress condition, cohesion and the angle of internal friction on the phenomenon of zonal disintegration is determined.

Titania nanotube arrays fabricated by anodic oxidation of titanium foil were calcined in dry nitrogen, air, and argon at various temperatures for varied period of time. Changes in morphology and crystallinity of the nanotube arrays were studied by means of SEM and XRD. The influences of annealing conditions on the electrochemical and conductivity were investigated by electrochemical impedance spectroscopy (EIS), and the results showed that the electrical conductivities of TiO2 nanotube arrays calcined in nitrogen for 3 h were improved greatly as compared to the as-grown titania nanotube arrays or annealed in air or argon. Well defined oxidation and reduction peaks were observed during the cyclic voltammetric scan at 0.1 V/s in 10 mM K3[Fe(CN)6] solution. Photocurrent response in TiO2 nanotube arrays calcined in nitrogen was significantly enhanced. Reduction of tetravalent titanium cations and the formation of oxygen vacancies were ascribed to explain the improved electrochemical and photoelectrical properties of titania nanotube arrays.

The computerized tomography (CT) images and CT values for the process of unloading, micro-cracking, and dilation up to the failure of limestone specimens under different unloading levels have been obtained by using the real-time CT technique. Clear CT images and CT value of the stages from compression of micro-cavities → emergence of micro-cracks → bifurcation → development → coalescence → suddenly collapse → rapid stress drop → unloading can be observed. The CT value, equivalent to rock density in the CT scan layer, is the most important parameter describing the damage evolution process of rock. The paper reveals that the mechanical behaviors of rock under unloading are different from those under loading due to its load-path dependency. It is clear from the experiment that it is easy for failure phenomenon of rock to happen suddenly under unloading. The mechanism of damage evolution of limestone is analyzed. Moreover, a damage model based on CT value and a new failure criterion are established.

A Ni/TiO 2 nanocomposite was successfully prepared by a pulse electrodeposition (PED) technique. Highly-ordered TiO 2 nanotube arrays fabricated by anodization were employed as a substrate and loaded with Ni nanoparticles by PED. The influence of pulse electrodeposition parameters was investigated on the morphology of nickel electrodeposits. The nanocomposite was characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The results indicated that Ni nanoparticles with average size ranging from 19 to 84 nm were obtained by changing electrodeposition parameters. At constant current off-time ( t off ) and pulse time of both negative and positive currents, the particle size decreased asymptotically with increasing amplitude of both negative and positive current. A progressive decrease of the particle size was observed with increasing current off-time at constant amplitude and pulse time of both negative and positive current. Increase in the deposition time at constant current off-time, amplitude and pulse time of both negative and positive current resulted in particle growth.