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Previous work showed that the copper oxide nanoparticles confined in titania nanotubes (Cu-in-TiO2NT) can effectively enhance the water–gas shift (WGS) activity. The WGS activity is directly related to the concentration of active copper species and oxygen vacancies (Ov). The addition of potassium is found to enhance WGS activity of copper catalysts to some extent. Herein, the K-promoted copper oxide (2 wt% Cu) nanoparticles confined in TiO2 nanotubes catalysts (Cu-in-K/TiO2NT) with different potassium contents were synthesized and investigated for the WGS reaction. The K-promoted catalysts exhibit the enhanced WGS activity. Especially, the Cu-in-K20/TiO2NT with the molar ratio of K/Cu = 20 displays twofold higher WGS activity compared with the Cu-in-TiO2NT. XRD, Raman, XPS, H2-TPR and in situ DRIFTS have verified that the addition of appropriate potassium can make active copper species bound with oxygen of the TiO2, leading to a partial reduction of TiO2 to TiO2-x, which is beneficial to form Cu–Ov–Ti site for the WGS reaction.

Construction of high-efficient and low-cost heterostructure photocatalyst is crucial for hydrogen production in solar driven water splitting. Herein, g-C3N4-modified TiO2 nanotubes (TNTs) with confined Pt nanoparticles were prepared via a facile two-step process. The results of structure characterizations by XRD, TEM, and XPS reveal that Pt nanoparticles with the average size of 2–3 nm are embedded in the inner cavity of the TiO2 nanotube, and amorphous g-C3N4 is attached to the outer wall of anatase TNTs. The as-prepared g-C3N4/TNTs@Pt ternary composite displays an enhanced visible light-induced absorbance capacity and improved charge carrier recombination rate than that of pure TNTs. The photocatalytic performance is evaluated by hydrogen evolution from water splitting by using methanol as sacrifice agent under solar light illumination. Compared with TNTs@Pt and g-C3N4/Pt photocatalysts, the as-prepared ternary nanocomposite exhibits the highest photocatalytic performance with a H2 evolution rate of 15.36 mmol h−1 g−1. A possible mechanism of photocatalytic H2 production over the ternary g-C3N4/TNTs@Pt composite is also proposed. This work not only provides a promising low-cost heterostructure candidate for water splitting, but also paves the way to rational design high-performance photocatalysts in solar-to-fuel conversion.

It is of great significance to develop water-gas shift (WGS) catalyst with high catalytic activity in low-temperature operational regime. In this paper, we have prepared Cu confined in TiO2 nanotub...

The single bubble behavior in a 3 mm rectangular gas–liquid–solid mini-fluidized bed with 90 μm particles was simulated using the combination of VOF and DEM, and the results were validated by experiments. The simulation on the expansion of liquid–solid mini-fluidized shows that the profiles of liquid and particle velocities are consistent, and both become more concentrated as the expansion ratio decreases. The bubble formation size does not change with the increase of the solid holdup from 0.25 to 0.45, while the bubble rise velocity becomes lower. The upward liquid velocity in the bubble wake exceeds 50% of the instantaneous bubble velocity. The size of the low particle concentration bubble wake reducing with the increase of solid holdup can be attributed to the decrease in the bubble rise velocity and the enhancement in the inertia effect of the liquid–solid flow.

Constructing uniform nanoceramic coating layers is a well-known challenge in the field of coating materials. Herein, Al2O3-coated Li[Li0.13Ni0.305Mn0.565]O2 (LLNM) Li-rich cathode materials are successfully prepared through a dry prilling coating (DPC) method. The structures and electrochemical performances of the Al2O3-coated products are systematically examined. Typically, the cycling stability is enhanced and voltage degradation upon cycling is reduced, benefiting from the unique and controllable nano-sized Al2O3 coating layer. Moreover, metal ion dissolution is avoided when using the DPC method, which is eco-friendly and suitable for large scale production.

The practical application of lithium-metal anodes in high-energy-density rechargeable lithium batteries is hindered by the uncontrolled growth of lithium dendrites and limited cycle life. An ether-based gel polymer electrolyte (GPE-H) is developed through in situ polymerization method, which has close contact with the electrode interface. Based on DFT calculations, it was confirmed that the cationic groups produced by polar solvent tris(1,1,1,3,3,3-hexafluoroisopropyl) (HFiP) initiate the ring-opening polymerization of DOL in the battery. As a result, GPE-H achieves considerable ionic conductivity (1.6 × 10-3 S cm-1) at ambient temperature, high lithium-ion transference number (tLi+ > 0.6) and an electrochemical stability window as high as 4.5 V. GPE-H can achieve up to 800 h uniform lithium plating/stripping at a current density of 1.65 mA cm-2 in Li symmetrical batteries. Li-S and LiFePO4 batteries using this GPE-H have long cycle performances at ambient temperature and high Coulomb efficiency (CE > 99.2%). From the above, in situ polymerized GPE-H electrolytes are promising candidates for high-energy-density rechargeable lithium batteries.

Oxidation of crotonaldehyde to crotonic acid is an important chemical reaction process because crotonic acid, its derivative and copolymer are ubiquitous in the productions of chemical, cosmetic, and medicines. However, the reactor safety and process efficiency are still not satisfactory. In order to solve such problems, a novel reactor of gas-liquid-solid mini-fluidized bed with bed inner diameter of 3 mm was developed to carry out the selective catalytic oxidation reaction. The effects of operation conditions and solid particle properties on the conversion rate of reactant crotonaldehyde and the selectivity of product crotonic acid were investigated. The causes of these effects are explained from the standpoint of residence time and gas-liquid mass transfer flux. Moreover, the comparison of reactor performance between the three-phase mini-fluidized bed and the batch stirred tank reactor as a traditional one was made to evaluate the performance of such a reactor. Experimental results show that the average reaction or conversion rate of the mini-fluidized bed is about 30 times much higher than that of batch stirred tank reactor to evaluate the improved performance. But the selectivity is less affected by the operation conditions and solid particle bed properties. The size reduction of three-phase mini-fluidized bed decreases the mass transfer distance of molecular diffusion, and the solid particles and mini-bubbles not only provide the higher specific interface area but also cause hydrodynamics changes that is to intensify the interface disturbance, which effectively accelerate the mass transfer.

Nd-modified Li-rich cathode materials (Li1.2Ni0.2Mn0.6O2) with different amounts are successfully prepared through a simple solid state reaction. The results indicate that Nd-modification could control the growth and compactness of the original particles. Additionally, at low temperature, Nd-modified Li1.2Ni0.2Mn0.6O2 shows good electrochemical performance. Benefiting from the unique structural features and synergistic effects of Nd, Li1.2(Ni0.2Mn0.6)1–xNdxO2 (x = 0.01) could stabilize the framework and suppress the decay of discharge voltage during the cycle process. As a result, Li1.2(Ni0.2Mn0.6)1–xNdxO2 (x = 0.01) cathode material shows a discharge capacity of 187.1 mA h g–1 (1 C) at 25 °C and 130.2 mA h g–1 (0.1 C) at −20 °C, which is considered as a new generation of cathode materials for lithium ion batteries.

Various renewable energy systems, such as water splitting cells and metal–air batteries, are based on the oxygen evolution reaction (OER). The replacement of common noble-metal platinum catalysts with highly efficient, cheap, and operationally stable electrocatalysts opens huge potential applications for OER; thus, there have been increasing efforts to develop alternative efficient OER catalysts via low-cost fabrication processes. Herein, we report a facile self-templated method to synthesize ZnCo–Fe core–shell nanocages derived from metal–organic frameworks (MOFs) as an efficient catalyst for OER. The unique structure of ZnCo–Fe core–shell nanocages offers a large active surface area with abundant active sites and efficient charge transfer capability as the hollow structure facilitates the active direct contact of materials with electrolytes. We introduced these catalysts at different ratios of Fe, which had a significant effect on the electrocatalytic performance of OER. In other words, the introduction of Fe not only changed the composition but also changed the morphology to expose numerous active sites for OER. Owing to the synergistic effect between the element composition and abundant active sites, the optimized ZnCo–Fe-20 sample presented a superior electrocatalytic OER performance with a very low overpotential (η = 176 mV at 10 mA cm−2) and a small Tafel slope (69.3 mV dec−1). This developed strategy can be easily extended to synthesize other MOF-derived polymetallic oxide-based hybrid electrodes for OER as a practical route for the design of cheap and efficient electrocatalysts.

Experiments on the gas-liquid-solid mini-fluidized beds with sizes of 1.45 and 2.3 mm show that the bed diameter has a considerable effect on the phase holdups and gas bubble size, because the macroscopic dimension (macro-scale) in a mini-fluidized bed is close to the dimensions of bubbles (meso-scale) and particles (micro-scale). Hence, the parameter of bed diameter was introduced through the modifications on the energy-minimization multi-scale (EMMS) model for the conventional three-phase mini-fluidized beds to predict the flow behavior of three-phase mini-fluidized bed. These modifications include two correction factors for the liquid and bubble slip velocities and a constraint condition on the bubble coalescence. The correction on the liquid slip velocity is to estimate the effect of column shear stress on the distribution of liquid velocity. The other correction factor is for quantifying the column resistance on the bubble rise. The correction factors were determined by the empirical correlations obtained from the experiments. Similarly, the bubble coalescence constraint is a correlation on the bubble spacing under steady state condition and determined from the experimental data. The modified meso-scale model equations were closed by this constraint condition and the solution of the model met the principle of energy minimization. The model predictions and experimental data agree well within the investigation range of experimental conditions.

Large-sized porous glucose-derived carbon (C) and graphene (G) co-modified LiFePO4 (LFP) composite microspheres (C@LFP/G) have been successfully in situ synthesized by one-pot solvothermal and followed annealing process using biological phytic acid (PhyA) as phosphorus source. The loose and porous microspheres with diameters in the range of 5–12 μm are self-assembled by carbon coated LFP nano particles along with randomly embedded/distributed graphene sheets. The effect of PhyA dosage and carbon modification on morphology and electrochemical properties were investigated. The results indicated that PhyA dosage plays an important role in construction of the self-assembled three-dimensional spherical microstructures during hydrothermal process. A reasonable assembly process elucidating the formation of the different structure is provided based on the experimental results. Additionally, the effects of carbon modification were also investigated, which reflected that the graphene and glucose-derived carbon personate a synergistic effect in regulating the size of LFP primary nanoparticles. The typical large-sized C@LFP/G microspheres composite exhibited the best electrochemical properties with the discharge specific capacity of 163.7 mA h g−1 at 0.1 C, excellent rate capability and cycling performance. This method may be extended to prepare other spherical olivine structured materials with large size as cathode materials for lithium-ion batteries.

A novel modified separator was synthesized with an ultraviolet irradiated polypropylene (PP) membrane and acrylonitrile monomers by a solution grafting reaction. It was demonstrated that polyacrylonitrile (PAN) was grafted on the PP separator surface by analyzing the results of FESEM, ATR–FTIR and XPS. The thermostability and wettability of the PAN-grafted PP (PP-g-PAN) separator were enhanced. Then, Li–S batteries were assembled using the modified separators. The cycling and rate capacity performance is improved clearly because of the higher liquid uptake, smaller porous size, better polysulfides absorption effect and interfacial affinity of the grafted separator. The modified separator can hinder the movement of Li2Sx effectively to prevent the shuttle effect of a Li–S battery. Therefore, this efficient method has great potential to be applied to the modification of other kinds of polymer membranes.

With the increasing demand for high-energy-density energy storage devices, lithium metal batteries have rekindled the interest of researchers due to ultra-high specific capacity. However, the extremely unstable interfaces between the electrolyte and electrodes limit its application seriously. Herein, we introduce an organosilicon compound, 1,3-Divinyltetramethyldisiloxane (DTMDS), as multifunctional electrolyte additive to enhance the performance of LiNi0.5Mn1.5O4/Li batteries. DTMDS contains two functional groups: siloxane groups (Si-O) and unsaturated carbon-carbon double bonds (CC). Siloxane groups can capture hydrogen fluoride (HF) in electrolyte, and the carbon-carbon double bonds can form thin and dense passivation layer on both cathode and anode surfaces by polymerization. As a result, the capacity retention of the batteries can retain more than 95% after 500 cycles. This work provides a valuable reference for the design of multifunctional additives and stabilizing the interfaces of high-voltage lithium metal batteries.

Highly efficient and stable catalysts for continuous catalytic ozonation of organic pollutants are of great significance in industrial applications. Perovskites have been seen as promising environmental catalysts because of their tunable defect structures and electronic properties. This work reports on A-site cation stoichiometry deviation as an effective engineering strategy to improve the crystallinity of perovskite CaZrO3, as well as its catalytic ozonation activity. High pure phase Ca1.1ZrO3 nanocrystals were successfully synthesized using a co-precipitation calcination method and evaluated as ozonation catalysts for m-cresol degradation. Surprisingly, Ca1.1ZrO3 exhibits a higher total organic carbon (TOC) removal rate, ozone utilization rate, and conversion rate of m-cresol than the stoichiometric of CaZrO3 and other conventional transition metal catalysts. In addition, Ca1.1ZrO3 shows an almost constant conversion rate of m-cresol (100%) and TOC removal rate (∼82%) during uninterrupted 100-h catalytic ozonation m-cresol degradation, demonstrating its excellent catalytic stability. These outstanding catalytic activity and stability toward ozonation are attributed to the synergistic meliorated oxygen octahedron structure, including Zr cation and contiguous coordinated oxygen, by introducing a non-stoichiometry defect into the perovskite. Thus, Ca1.1ZrO3 presents an advanced oxidation process of reactive oxygen species (·OH, O2·-, 1O2). These results were verified by in situ X-ray diffraction, in situ Fourier transform infrared spectroscopy, electron paramagnetic resonance, and density functional theory. This work strongly believes that Ca1.1ZrO3 can be an efficient, stable, and an economic catalyst for catalytic ozonation.

Previous simulations of three-phase fluidization systems based on the Euler-Lagrange approach have made progress in the studies of bubble and suspension dynamics. However, for guiding the operation and design of reactors, it is obviously more practical to obtain the phase holdup characteristics under the steady state. In this study, the hydrodynamic simulations on the gas–liquid-solid mini-fluidized beds (GLS-mFBs) were performed from the initial introduction of bubbling flow to the steady three-phase fluidization using the coupling model of volume of fluid (VOF) and discrete element method (DEM). After the initial process of bubbling flow accompanied by redistribution of phase holdups, i.e., the contraction of fluidized bed, the steady state of the GLS-mFB was achieved and maintained by the interactions between bubbles and fluidized bed. The axial and radial profiles of phase holdups in the steady GLS-mFBs, which is difficult to measure through experiments, are obtained and discussed. It is found that the suspension resistance against the rising bubbles is strengthened by the wall confining effect arising from the shrinkage of bubble-wall gap under smaller column diameter, and the phase holdup characteristics and bubble dynamics are investigated and explained by this effect. The bubble wake, which plays an important role in the momentum exchange between bubbles and suspension, is analyzed in terms of formation mechanism and size changes. It is proved that the VOF-DEM simulation is an effective method to predict the phase holdups of the GLS-mFBs and explain the underlying hydrodynamic mechanism.

Exploring earth-abundant and cost-effective catalysts with high activity and stability for a hydrogen evolution reaction (HER) is of great importance to practical applications of alkaline water electrolysis. Here, we report on A-site Ba2+-deficiency doping as an effective strategy to enhance the electrochemical activity of BaCo0.4Fe0.4Zr0.1Y0.1O3−δ for HER, which is related to the formation of oxygen vacancies around active Co/Fe ions. By comparison with the benchmarking Ba0.5Sr0.5Co0.8Fe0.2O3−δ, one of the most spotlighted perovskite oxides, the Ba0.95Co0.4Fe0.4Zr0.1Y0.1O3−δ oxide has lower overpotential and smaller Tafel slope. Furthermore, the Ba0.95Co0.4Fe0.4Zr0.1Y0.1O3−δ catalyst is ultrastable in an alkaline solution. The enhanced HER performance originated from the increased active atoms adjacent to oxygen vacancies on the surface of the Ba0.95Co0.4Fe0.4Zr0.1Y0.1O3−δ catalyst induced by Ba2+-deficiency doping. The low-coordinated active atoms and adjacent oxygen ions may play the role of heterojunctions that synergistically facilitate the Volmer process and thus render stimulated HER catalytic activity. The preliminary results suggest that Ba2+-deficiency doping is a feasible method to tailor the physical and electrochemical properties of perovskite, and that Ba0.95Co0.4Fe0.4Zr0.1Y0.1O3−δ is a potential catalyst for HER.

Perovskite oxides with mixed electronic-ionic conduction are important catalysts for the oxygen reduction reaction in solid oxide fuel cells (SOFCs). Here, two cobalt-free perovskite oxides, LaFe0.8Cu0.2O3-δ (LFCuO) and BaFe0.8Cu0.2O3-δ (BFCuO), were synthesized and comparatively studied with respect to their phase structures, oxygen contents, chemical defects, thermal expansion coefficient (TEC), as well as electrical and electrochemical properties. Different structures and properties have been found for each oxide, which have been interpreted based on their tolerance factors and chemical defects. LFCuO showed much better overall performance than BFCuO, and it proved to be a promising cobalt-free cathode material of intermediate-temperature SOFCs with a low TEC (12.0×10-6 °C-1) that matches well with TECs of the electrolytes, high catalytic activity for the oxygen reduction reaction characterized by low area specific resistances (0.090 Ω cm2 at 800 °C and 0.20 Ω cm2 at 750 °C), and high-temperature chemical stability with electrolytes.

Flow regimes and their transitions in the gas-liquid-solid mini-fluidized beds (MFBs) with single gas orifice were studied experimentally in this paper. The diameter of the fluidized beds varied from 3 mm to 5 mm and the vertical column height was 50 mm. The ranges of superficial gas velocity and liquid velocity were 1.96 × 10−4–4.73 × 10−3 m/s and 5 × 10−6–4.2 × 10−2 m/s, respectively. The solid particles ranged in size from 50 μm to 300 μm. Half-fluidization, slug, dispersed bubble and transport flow regimes in the three-phase MFBs were identified by analyzing minimum fluidization velocity, pressure drop, and entrainment velocity of solid particles based on experimental data of pressure drop and fluidization velocity as well as flow observations. The effects of solid particle, liquid properties, bed, gas orifice sizes, and static bed height on the flow regimes and transitions were investigated. Results showed that the behavior of gas bubbles and the wall effect affected the flow regimes and transitions. Obvious wall effect increased minimum fluidization liquid velocity in the liquid-solid mini-fluidized beds, which increased the transition liquid velocity from the half-fluidization to slug flow regimes. Moreover, wall effect made Taylor bubbles bigger at lower superficial liquid velocities due to the bubble coalescence and the transition boundaries expansion. Solid particles aggregation, wall effect and bubble wake behavior were responsible for increment of the minimum entrainment velocity of solid particles. Flow regime maps of the gas-liquid-solid MFBs were presented and correlations were suggested for the flow regime boundaries.

The bed-expansion characteristics of liquid–solid micro-fluidized beds were experimentally studied. Bed columns with inner diameters of 0.8, 1.45, and 2.3 mm were fabricated based on capillaries. Five particle sizes in a range of 22–58 μm were investigated. Bed-expansion curves were plotted using visually recorded bed-expansion heights. The bed expansion and initial fluidization behavior were compared with predictions for conventional-scale beds. Evident differences are reflected in lower expansion ratios and higher minimum fluidization velocities for micro-fluidized beds. These were attributed to the increase in the internal surface area of the particle beds and specific surface area of wall contact. The wall effect for micro-fluidized beds at higher particle/bed diameter ratios caused higher local voidage and an increase in expansion ratio. Correlations for the exponent and proportional coefficient in the Richardson–Zaki equation for micro-fluidized beds were proposed. The minimum fluidization velocities were correlated using a modification of the Ergun equation.

Although great efforts have been devoted to enhancing the efficiency and stability of perovskite solar cells (PSCs), the performance of PSCs has been far lower than anticipated. Interface engineering is helpful for obtaining high efficiency and stability through control of the interfacial charge transfer in PSCs. This paper demonstrates that the efficiency and stability of PSCs can be enhanced by introducing stable α-CsPbI3 quantum dots (QDs) as an interface layer between the perovskite film and the hole transport material (HTM) layer. By synergistically controlling the valence band position (VBP) of the perovskite and the interface layer, an interface engineering strategy was successfully used to increase the efficiency of hole transfer from the perovskite to the HTM layer, resulting in the power conversion efficiency increasing from 15.17 to 18.56%. In addition, the enhancement of the stability of PSCs can be attributed to coating inorganic CsPbI3 QDs onto the perovskite layer, which have a high moisture stability and result in long-term stability of the PSCs in ambient air.

A delicate control of crystallization and morphology of perovskite absorbers is critical to obtain high performance hybrid perovskite solar cells (PSCs). Here, we have developed a novel crystallization strategy which involves hydration water induced intermediate phase formation under heat assisted spin-coating processing (HASP) to manipulate the morphology and grain size of perovskite films, and thus it can avoid the use of toxic and volatile antisolvents used in conventional one-step solution processes to make PSCs. During HASP, impressive morphological evolution of films occurs with the formation of CH3NH3PbI3·xH2O perovskite intermediate phases. With ingenious control of the crystallization kinetics, highly crystalline perovskite films with fewer defect states and high carrier lifetimes are obtained. The corresponding PSCs exhibit a power conversion efficiency (PCE) of 19.12% with a stabilized power output efficiency of 18.89% at the maximum power point, which is a 70% enhancement compared to that of conventional one-step process based PSCs. Furthermore, the PSC fabricated by the HASP method achieved a PCE of 15.47% with an active area of 1.2 cm2. Moreover, the flexible PSCs fabricated by the HASP method achieved a record efficiency of 14.87% with negligible hysteresis for PEDOT:PSS-based flexible inverted PSCs. Our work opens up a new avenue for morphology and crystallization control through hydration water induced intermediate phase formation under HASP, which paves the way toward further enhancing the device performance of perovskite solar cells.

A poly(propylene carbonate) (PPC)-based sandwich-like composite solid polymer electrolyte (SE) was designed and applied to solid-state lithium ion batteries at 25 °C. The sandwich-like structure of the composite SE was composed of three parts. A polypropylene separator was used as a support membrane to enhance the strength of the SE membrane. Succinonitrile in the PPC-based SE was used to increase the ionic conductivity. Pure PPC as a buffer layer was closed to the lithium anode, which could improve the interface compatibility, Coulombic efficiency, and cycle life of batteries. The sandwich-like composite SE exhibited good comprehensive properties such as a high ion transference number (0.65), sufficient ionic conductivity (2.18 × 10–4 S cm–1 and 5.77 × 10–4 S cm–1 at 25 and 55 °C, respectively), and outstanding electrochemical stability at ambient temperature. Furthermore, a Li/LiFePO4 cell with the sandwich-like composite SE delivered a discharge capacity close to 140 mA h g–1 (0.1 C) at 25 °C. The resu...

Zn2SnO4@C/Sn composites were synthesized via the rapid calcination of a zinc-tin binary MOF under a reducing atmosphere for 1 min. Nanometal Sn, which has a good conductivity, and Zn2SnO4 nanoparticles were assembled into secondary particles in the synthesized composites. The metal Sn acted as an active material and a conductive agent. The nanosized Zn2SnO4@C/Sn composites reduced the volume expansion and enhanced the electrochemical performance. Additionally, the carbon provided buffer spaces for the volume expansion of the active material. The metal Sn grew into large particles as the calcination time increased, which transformed the lithium storage process from surface controlled to diffusion controlled. When the Zn2SnO4@C/Sn composites were used as anode materials for LIBs, a superior electrochemical performance was achieved. A reversible capacity of up to 1140 mA h g−1 was obtained at a current density of 100 mA g−1 after 100 cycles. The reason for the capacity fading in the samples that were calcined for a long time was also analyzed, and the results might be helpful for researchers when designing new anode materials.

The structural stability of LiCoO2 at high voltage is a crucial concern of LiCoO2 electrode. The experiment in this work have proved that mixed LiCoO2 and LiFePO4 electrode can stabilize the layered structure of LiCoO2 and improve their cycle stability significantly. The SEM images show that a protective thin film was gradually formed on the surface of LiCoO2 particles during charging and discharging. With the amount of mixed LiFePO4 increasing, the film increases, which inhibits the broken of the LiCoO2 particles and the formation of Co3O4; The battery built using the mixed LiCoO2 and LiFePO4 electrodes shows the best cycle stability when the content of LiFePO4 is 12 wt%, with the initial discharge specific capacity of 177.9 mA h g−1 and the capacity retention of 77.2% after 200 cycles between 3.0 and 4.5 V at 0.2 C.

A unique technique is present to synthesize three dimensional hierarchical vanadium oxides/reduced graphene oxide composites (denoted as 3D VO x /rGO composites) by laser irradiation over the mixture of V 2 O 5 nanobelts and GO nanosheets. Electron microscopy and X-ray photoelectron spectroscopy (XPS) examinations reveal that polydisperse V 2 O 5 /VO 2 heterostructured nanoparticles form strong coupling with rGO. As a result, a specific capacitance of 252 F g −1 is achieved for 3D VO x /rGO composites when used as supercapacitor electrodes, and the capacitance can retain 92% of the initial specific capacitance even after 10000 cycles at a current density of 100 A g −1 . The improvement of supercapacitor performance is achieved by significantly increase on specific surface area of 3D VO x /rGO composites, which favors the easy access of the electrolyte and provides large electroactive surface, and strong V O C bond between VO x nanoparticles and rGO, which benefits the effective charge transfer. We believe that the facile laser irradiation approach represents a major step not only for the simple and efficient fabrication of high performance electrodes but also in the practical application of laser processing to synthesize other functional hierarchical nanocomposites.

The electronic environment and physicochemical property of carbon materials can be easily tailored and modulated by heteroatom doping. Herein, we demonstrate that net-like N, O, S triple-doped microporous carbon nanowires (NOS-MCNs) as an anode can be designed to improve the electrochemical performance of sodium ion batteries. Ammonium persulfate as oxidant can also provide a nitrogen and sulfur source for S-containing PPy. The N, O and S atoms are introduced into the carbon skeleton with activation and carbonization processes to modify the surface properties. As an anode, the material exhibits a high specific capacity and a long lifespan (≈301 mA h g−1 at 0.2 A g−1 after 1000 cycles) as well as an excellent rate capability (158 mA h g−1 at an extremely high current density of 10 A g−1). This work offers a facile strategy to synthesize triple-doped porous carbon materials for sodium ion batteries and other energy-storage fields.

N-Doped 3D bubble-like porous graphene was synthesized via a simple template directed method using polystyrene nanospheres as a template and low-cost industrial melamine as the nitrogen source. The as-synthesized N-3DPGX possessed a high specific surface area, uniform and controllable porous structure and high nitrogen doping content. Benefiting from these features, the as-obtained N-3DPG4 as an anode for sodium ion batteries delivered a high specific capacity of 310 mA h g−1 after 500 cycles at a current density of 0.2 A g−1, and also excellent rate capability as high as 169 mA h g−1 at 10 A g−1. This simple synthetic method, unique porous structure and outstanding electrochemical performance demonstrated that N-3DPG is a promising candidate for application in sodium ion batteries for large-scale electrochemical energy storage.

Hard carbon exhibits high theoretical capacity for sodium-ion batteries. However, its practical application suffers from low electric conductivity, poor electrochemical stability, and sluggish kinetics. To tackle these challenges, novel nitrogen-doped carbon spheres with mesopores, ultrathin nanostructure, and optimal graphitization are prepared by a three-step procedure. We find that the as-prepared sample (NMCSs-800) with an optimal structure and nitrogen content delivers a high reversible sodium storage capacity of 334.7 mA h/g at 50 mA/g and an ultrahigh rate performance of 93.9 mA h/g at 5 A/g, which is better than most state-of-the-art carbon materials. The improved energy storage capacity is attributed to its unique architecture and optimal nitrogen doping, which provide abundant active sites, defects, and voids. Moreover, kinetic analysis and in situ Raman spectroscopy results reveal adsorption and adsorption-intercalation mechanisms for Na

1.5-1.6 eV bandgap Pb-based perovskite solar cells (PSCs) with 30-31% theoretical efficiency limit by the Shockley-Queisser model achieve 21-24% power conversion efficiencies (PCEs). However, the best PCEs of reported ideal-bandgap (1.3-1.4 eV) Sn-Pb PSCs with a higher 33% theoretical efficiency limit are 0.4 V). Herein, it is found that the addition of guanidinium bromide (GABr) can significantly improve the structural and photoelectric characteristics of ideal-bandgap (≈1.34 eV) Sn-Pb perovskite films. GABr introduced in the perovskite films can efficiently reduce the high defect density caused by Sn2+ oxidation in the perovskite, which is favorable for facilitating hole transport, decreasing charge-carrier recombination, and reducing the Voc deficit. Therefore, the best PCE of 20.63% with a certificated efficiency of 19.8% is achieved in 1.35 eV PSCs, along with a record small Voc deficit of 0.33 V, which is the highest PCE among all values reported to date for ideal-bandgap Sn-Pb PSCs. Moreover, the GABr-modified PSCs exhibit significantly improved environmental and thermal stability. This work represents a noteworthy step toward the fabrication of efficient and stable ideal-bandgap PSCs.

A free-standing LiFePO4/carbon nanofiber hybrid (LFP/CF) electrode with (010)-oriented LiFePO4 nanocrystals was in-situ constructed by a one-pot electrospinning method. It is found that poly (vinylpyrrolidone) (PVP) can regulate the growth of (010)-face-orientated LiFePO4 crystals partly. As a model material, the optimal (010)-manifest LiFePO4/carbon nanofibers cathode exhibits a discharge capacity of 152 mA h g−1 at 0.5C after 500 cycles with capacity retention of 98.2% and superior rate performance of 108.6 mA h g−1 at 5C. The excellent performance can be ascribed to the well-designed 3D conductive network, fast Li-ion diffusion path, and porous structure for electrolyte penetration. This route provides an efficiency strategy with low cost and one-step process for the preparation of free-standing (010)-manifest LiFePO4/carbon nanofiber cathode material, and can also be extended to other olivine materials.

The problem of Li-O2 batteries lies in the lack of high performance and low-cost catalyst that can promote the decomposition of discharge products. The trouble is even more serious when it cycles in CO2. Herein, we synthesize a nitrogen (N) and sulfur (S) co-doped 3D graphene@NiO (N,S-3DG@NiO) composite as a bi-functional electrode catalyst, which can concurrently support the stable cycling of Li-O2 and Li-CO2 batteries. In this design, the N, S-3DG@NiO has three-dimensional porous structure, which can provide extra storage space for discharge products, and N and S co-doping provides more reaction active sites. The bi-functional electrode catalyst delivers a high discharge capacity of 17300 mAh g-1 and excellent cyclability (more than 50 cycles, limited capacity 500 mA g-1) when it is applied for Li-O2 batteries. In addition, the N, S-3DG@NiO catalyst also exhibits a large discharge capacity of 13400 mAh g-1 when it is used as cathode for Li-CO2 batteries (more than 50 cycles, limited capacity 500 mA g-1). This study not only provides a high efficiency bi-functional cathode catalyst for Li-O2 and Li-CO2 batteries, but also promotes the development of high specific energy batteries.

Ba0.5Sr0.5Co0.8Fe0.2O3-δ is a well-known cathode material of intermediate-temperature solid oxide fuel cell. To elucidate its electrical and electrochemical properties, three chemical defect models were adopted in this work for fitting the data of oxygen stoichiometry and electrical conductivities as a function of temperature. Reasonable values of concentrations and mobility of charge carriers, and were obtained with the cluster defect model. The p-type electronic conductivities and oxygen ionic conductivities were separated from the total electrical conductivities. The temperature-dependence of oxygen vacancy diffusion coefficient of BSCF were also obtained, and the results were comparable with the data measured experimentally.

Double-layered perovskite oxides of Pr1−yBaCo2O5+δ (P1−yBCO) with A-site Pr3+-deficiency contents of y = 0.00–0.10 have been studied with respect to phase structures, oxygen content, high-temperature chemical stabilities as well as electrical and electrochemical properties as cathode materials of intermediate-temperature solid oxide fuel cells (IT-SOFCs). The Pr3+-deficiency content in P1−yBCO is limited by ∼8 mol%, and the Pr3+-deficiency hardly changes lattice parameters of P1−yBCO. Content of oxygen vacancies increases while that of Co4+ decreases with the higher Pr3+-deficiency content. P1−yBCO is chemically stable with the Gd0.1Ce0.9O1.95 (GDC) electrolyte at 1100 °C and below in air. Introduction of Pr3+-deficiency decreases electrical conductivities and significantly improves electrochemical performance of P1−yBCO. Among the studied oxides, P0.95BCO with 5 mol% Pr3+-deficiency shows the best electrochemical performance with low ASR values of 0.113 Ω cm2 at 600 °C, 0.054 Ω cm2 at 650 °C and 0.028 Ω cm2 at 700 °C respectively, demonstrating it a promising cathode material of IT-SOFCs. The results of P1−yBCO have also been compared with those of Ba2+-deficient PrBa1−xCo2O5+δ (PB1−xCO, x = 0.00–0.10) oxides and major differences have been found in lattice parameters, oxygen content, chemical defects, electrical conductivities and ASR results. Factors contributing to these differences have been discussed.

Pr 0.83 BaCo 1.33 Sc 0.5 O 6−δ –0.17PrCoO 3 (PBCS-0.17PCO) nano-composite material has been synthesized by a combined EDTA-citrate complexing sol–gel method, and characterized as cathode material of intermediate-temperature solid oxide fuel cell (IT-SOFC). Phase structure has been characterized by X-ray diffraction (XRD) measurement. The results indicate that the composite material is composed of two cubic perovskite phases with nano-scaled grain sizes. Thermal expansion coefficient (TEC) of the composite material was measured to be 18.4 × 10 −6 /°C at temperatures of 30–900 °C. Electrical conductivities were measured in air by DC four-electrode method, and the conductivity values increase monotonically with the higher temperatures from 100 °C up to 750 °C. Electrochemical performance of the PBCS-0.17PCO composite materials was studied by electrochemical impedance spectra (EIS) measurements using GDC-based symmetric cell. Low area specific resistance (ASR) values ranging from 0.127 Ω cm 2 at 600 °C, 0.069 Ω cm 2 at 650 °C, 0.039 Ω cm 2 at 700 °C to 0.026 Ω cm 2 at 750 °C were achieved for the composite cathode, demonstrating its promising application in IT-SOFCs.

Double-layered perovskite oxides of Sm1−xBaCo2O5+δ (S1−xBCO) with various A-site Sm3+-deficiencies (x = 0.00–0.08) were synthesized and evaluated as cathode materials of intermediate-temperature solid oxide fuel cells (IT-SOFCs). The Sm3+-deficiency content in S1−xBCO was limited up to x = 0.05, and higher content x = 0.08 caused impurity phase. S1−xBCO oxides were chemically stable with GDC electrolyte at 1050 °C and below. Introduction of Sm3+-deficiency caused decreased oxygen content and increased concentration of oxygen vacancy in S1−xBCO. Electrical conductivities of S1−xBCO decreased with increasing temperature in air, and also changed with the Sm3+-deficiency content. Electrochemical performance of S1−xBCO cathodes were characterized by impedance spectra measurement based on symmetric cells. Higher Sm3+ deficiency content has resulted in decreased area specific resistances (ASRs) and activation energy (Ea), i.e. enhanced electrochemical reaction reactivity for the S1−xBCO cathodes. Among the studied samples, the S0.95BCO (x = 0.05) oxide showed the best electrochemical performance with ASR values of 0.316 Ω cm2 at 600 °C, 0.137 Ω cm2 at 650 °C, 0.068 Ω cm2 at 700 °C and 0.038 Ω cm2 at 750 °C respectively, thus it's a promising cathode material of IT-SOFCs.

The surface defects and grain boundary defects of organometallic halide perovskite films are detrimental to both the efficiency and stability of perovskite solar cells (PSCs). Furthermore, the electrical conductivity, work function and surface morphology of the hole transport layer (HTL) can also affect the performance of PSCs significantly. Here, we first have developed a novel synergistic strategy that uses multiple functional EMIC (1-Ethyl-3-methylimidazolium chloride) ionic liquid to modify PEDOT:PSS (poly (3, 4-ethylenedioxythiophene) polystyrene sulfonate) HTL, thereby obtaining the HTL with high electrical conductivity, low work function and smooth surface. Moreover, a novel S-acetylthiocholine chloride molecule which replaces expensive PCBM (phenyl-C61-butyric acid methyl ester) is developed to effectively passivate the negative- and positive-charged ionic defects in hybrid perovskite. The synergistic strategy extends the carrier recombination lifetime and reduces the charge trap density. In addition, the current hysteresis of the inverted device was also effectively eliminated. As a result, the champion cell in small area shows 20.06% efficiency with no hysteresis, along with an efficiency 18.77% for inverted PSCs in an active area of 1 cm2, both of which are the highest efficiency in the one-step PEDOT:PSS-based inverted PSCs so far. Compared to PCBM, the device passivated by S-acetylthiocholine chloride also has improved environmental stability (retaining 85% of initial PCE after 35 days storage without encapsulation in air with 60% humidity) and thermal stability (retaining 87% of initial PCE after 80 °C for 24 h storage without encapsulation under inert atmosphere).

Phase structure, structure stability, electrical properties and catalytic activity for oxygen reduction reaction of the Ba-deficient layered-perovskite oxides LaBa1-xCo2O5+delta (LB1-xCO, x = 0.00-0.15) have been studied to determine their viability as cathode material of intermediate-temperature solid oxide fuel cells (IT-SOFCs). LB1-xCO had tetragonal layered-perovskite structure when calcined at 850 degrees C-1050 degrees C in air but transformed into cubic structure at higher temperatures. The LB1-xCO oxide exhibited lower electrical conductivities and decreased area-specific resistances (ASRs) on the Ce0.9Gd0.1O1.95 (GDC) electrolyte with higher Ba-deficiency content. Among the samples, the LB0.90CO (x = 0.10) oxide exhibited the best electrochemical performance with ASR values of 0.118 Omega cm(2) at 600 degrees C and 0.023 Omega cm(2) at 700 degrees C respectively, similar to 40% lower than the results of the parent oxide (x = 0), demonstrating its promising application as cathode materials of IT-SOFCs. (C) 2013 Elsevier B.V. All rights reserved.

Cu–C co-coated LiFePO4 (LiFePO4/(C + Cu)) cathode material was successfully prepared through solid state reduction reaction. The optimized additive amount of CuO was determined by electrochemical test of series content-dependent samples. Electrochemical performances of LiFePO4/(C + Cu) cathode material were investigated. Crystalline structure, morphology and electrochemical performance of the samples were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), charge–discharge tests and AC impedance techniques. Results showed that crystal structure of the bulk material was not destroyed after Cu particles distributed on the surface of LiFePO4/C. With 5 wt% CuO additive, the LiFePO4/(C + Cu) cathode material showed improved electrochemical performance especially at high rates and low temperature. At 25 °C and 0.1 C current rate, specific capacity of the Cu-coated sample reaches 161.3 mA h/g. The result was 47 mA h/g higher than that of the un-coated one. At −20 °C, the discharge capacity of Cu-coated materials was 113.4 mA h/g at 0.1 C rate and 83.8 mA h/g at 5 C rate, which reached about 70% of that at room temperature, respectively.

GdBaCo2O5+delta (GBCO)/poly (vinyl pyrrolidone) (PVP) composite nanofibers were prepared by electrospinning. Structural and morphological evolution of the GBCO/PVP fibers under calcinations at various temperatures was studied. Using 600 degrees C pre-calcined GBCO/PVP composite nanofibers, pure phase GBCO cathode with homogeneous network structure was easily fabricated on Ce0.9Gd0.1O1.95 (GDC) electrolyte. The as-prepared GBCO cathode was characterized by electrochemical impedance spectra (EIS) measurements based on a GBCO/GDC/GBCO symmetric cell. Its electrochemical performance was compared with the cathode prepared with the GBCO powders synthesized with sol-gel method. The GBCO cathode fabricated using GBCO/PVP composite fibers had area specific resistances (ASRs) of 0.53 Omega cm(2) at 600 degrees C, 0.22 Omega cm(2) at 650 degrees C, 0.10 Omega cm(2) at 700 degrees C and 0.043 Omega cm(2) at 750 degrees C respectively, which are lower than ASR results of the GBCO cathode prepared with powders. The results have demonstrated that the GBCO cathode fabricated using electrospun composite nanofibers has significantly enhanced electrochemical activities for oxygen reduction reaction, and it can serve as a promising cathode material for intermediate- temperature solid oxide fuel cell. (c) 2013 Elsevier B.V. All rights reserved.

A-site cation-ordered perovskite oxide LaBaCo 2 O 5+δ (LBCO) was synthesized and evaluated as a cathode material of intermediate-temperature solid oxide fuel cells (IT-SOFCs). LBCO was structurally stable when calcined at 850 °C in air but transformed into cation-disordered structure at 1050 °C. LBCO showed chemical compatibility with Gd 0.1 Ce 0.9 O 1.95 (GDC) electrolyte at 850 °C and 1000 °C in air. Conductivity of LBCO firstly increased slightly with higher temperature to a maximum of 470 S cm −1 at ∼250 °C and then decreased gradually with further increase in temperature. Electrochemical impedance spectra of the LBCO/GDC/LBCO symmetric cell were measured, and electrode reaction mechanism for the LBCO cathode was analyzed. The electrode polarization resistance of LBCO was mainly contributed by oxygen ionic transfer across the cathode/electrolyte interface and oxygen atom diffusion-electronic charge transfer process. Low area-specific resistances with values ranging from 0.15 Ω cm 2 at 650 °C to 0.0086 Ω cm 2 at 800 °C were obtained. These results have demonstrated that the A-site cation-ordered perovskite oxide LBCO is a promising cathode material for IT-SOFCs.

A-site Ba-deficient PrBa1−xCo2O5+δ (PB1−xCO, x = 0–0.08) oxides are synthesized and evaluated as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs) with respect to crystal structure, chemical stability, thermal expansion behavior, electrical conduction and electrochemical performance. PB1−xCO with Ba-deficiency x = 0–0.08 has an orthorhombic structure, which shows lattice shrinkage with bigger x; higher Ba-deficiency x = 0.1 causes formation of impurity phases. The PB1−xCO oxides are chemically stable with Gd0.1Ce0.9O1.95 (GDC) electrolyte at 1050 °C in air. Thermal expansion coefficient of PB1−xCO decreases slightly with higher Ba-deficiency. Electrical conductivity of PB1−xCO exhibits an initial decrease with higher Ba deficiency to x = 0.03 and then increases gradually to a maximum at x = 0.08. Introduction of Ba deficiency greatly improves electrochemical performance of PB1−xCO, characterized by decreased area specific resistances (ASRs) with higher Ba deficiency. The ASR values as low as 0.115 Ω cm2 and 0.093 Ω cm2 have been obtained at 600 °C in air for PB1−xCO with x = 0.05 and 0.08 respectively. These results have demonstrated that the Ba-deficient PB1−xCO (x = 0.03–0.08) oxides are promising cathode materials for IT-SOFCs.

An A-site Ba cation-deficient layered-perovskite oxide PrBa 0.92 Co 2 O 5+δ (PB 0.92 CO) was evaluated as a new cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). PB 0.92 CO is chemically stable with Ce 0.9 Gd 0.1 O 1.95 (GDC) electrolyte at temperatures up to 1100 °C. PB 0.92 CO has conductivities of 580–195 S cm −1 at temperatures of 200–800 °C in air. Area specific resistances (ASR) of PB 0.92 CO cathode on the GDC electrolyte layer range from 0.093 Ω cm 2 at 600 °C to 0.0068 Ω cm 2 at 800 °C with an activation energy of 1.05 eV. These ASR values are much lower than the results of the parent PrBaCo 2 O 5+δ (PBCO) cathode, cation-doped PBCO cathodes and the PBCO-based composite cathodes. The preliminary results have demonstrated that PB 0.92 CO has excellent electrochemical performances at temperatures of 600 °C–800 °C and is a very promising cathode material for IT-SOFCs.

Cubic perovskite oxide La 0.5 Ba 0.5 CoO 3−δ (LBCO) and its composite with Gd 0.1 Ce 0.9 O 1.95 (GDC) electrolyte, LBCO–GDC in 1:1 weight ratio were prepared. Chemical compatibility between LBCO and GDC was studied and no serious phase reaction occurred at temperatures up to 1050 °C in air. Electrochemical performance of the cathodes was measured by Electrochemical Impedance Spectroscopy (EIS) as a function of temperature and oxygen partial pressure. Electrode reaction mechanism was analyzed based on fitting results of the EIS with proper equivalent circuit models. Comparison of the results demonstrated that introduction of the ionic conductive GDC component to the LBCO–GDC composite cathode hardly influenced gas diffusion through bulk of the cathode (low-frequency process) while greatly enhanced oxygen ionic transfer across the cathode/electrolyte interface (high-frequency process) and the electrode reaction occurring in the medium-frequency range. As a result, the LBCO–GDC composite cathode exhibited lower area-specific resistance (ASR) than the LBCO cathode, with ASR value ranging from ∼0.12 Ω cm 2 at 600 °C to ∼0.01 Ω cm 2 at 800 °C. These results have demonstrated that the LBCO–GDC composite (1:1 weight ratio) is highly promising as a cathode for intermediate temperature solid oxide fuel cell.