Jianbao Li

Photocatalytic Degradation of Methyl Orange Using a TiO2/Ti Mesh Electrode with 3D Nanotube Arrays

To further improve the photocatalytic techniques for water purification and wastewater treatment, we successfully prepared a new type of TiO(2)/Ti mesh photoelectrode, by anodization in ethylene glycol solution. The three-dimensional arrays of nanotubes formed on Ti mesh show a significant improvement in photocatalytic activity, compared to the nanotube arrays formed on foil. This can be demonstrated by about 22 and 38% enhancement in the degradation efficiency per mass and per area, respectively, when TiO(2)/Ti mesh electrode was used to photocatalyze methyl orange (MO). Furthermore, the effects of different parameters on MO photodegradation were investigated, such as different photoelectrode calcination temperature, the initial pH value of MO solution, and the present of hydrogen peroxide. The superior photocatalytic activity could be achieved by the TiO(2)/Ti mesh photoelectrode calcinated at 550 °C, due to the appearance of mixed crystal phases of anatase and rutile. In strong acidic or caustic conditions, such as pH 1 or 13, a high degradation efficiency can be both obtained. The presence of H(2)O(2) in photocatalytic reactions can promote photocatalytic degradation efficiencies. Moreover, the experimental results demonstrated the excellent stability and reliability of the TiO(2)/Ti mesh electrode.

Ru0.01Ti0.99Nb2O7 as an intercalation-type anode material with a large capacity and high rate performance for lithium-ion batteries

RuxTi1−xNb2O7 (x = 0 and 0.01) materials have been synthesized via a solid-state reaction method. X-ray diffraction combined with Rietveld refinements demonstrates that both samples have a Wadsley–Roth shear structure with a C2/m space group without any impurities, and that the unit cell volume increases after the trace Ru4+ doping. Scanning electron microscopy and specific surface area tests reveal that the Ru4+ doping decreases the average particle size. The Li+ ion diffusion coefficient and electronic conductivity of Ru0.01Ti0.99Nb2O7 are respectively 64% and at least two orders of magnitude larger than those of the pristine TiNb2O7. First-principles calculations show that the increased electronic conductivity can result from the formation of impurity bands after the Ru4+ doping. Ru0.01Ti0.99Nb2O7 exhibits a large initial discharge capacity of 351 mA h g−1 at 0.1 C between 3.0 and 0.8 V vs. Li/Li+, approaching its theoretical capacity (388 mA h g−1). At 5 C, unlike the pristine TiNb2O7 with a small charge capacity of 115 mA h g−1, Ru0.01Ti0.99Nb2O7 delivers a large value of 181 mA h g−1, even exceeding the theoretical capacity of the popular spinel Li4Ti5O12 (175 mA h g−1). After 100 cycles, Ru0.01Ti0.99Nb2O7 shows a large capacity retention of 90.1%. These outstanding electrochemical performances can be attributed to its improved Li+ ionic and electronic conductivity as well as smaller particle size.

Nitrogen-Doped TiO2 Nanotube Arrays with Enhanced Photoelectrochemical Property

N-doped TiO2 nanotube arrays were prepared by electrochemical anodization in glycerol electrolyte, followed by electrochemical deposition in NH4Cl solution. An orthogonal experiment was used to optimize the doping conditions. Electrolyte concentration, reaction voltage, and reaction time were the main factors to influence the N-doping effect which was the determinant of the visible range photoresponse. The optimal N-doping conditions were determined as follows: reaction voltage is 3 V, reaction time is 2 h, and electrolyte concentration is 0.5 M. The maximal photocurrent enhanced ratio was 30% under white-light irradiation. About 58% improvement of photocatalytic efficiency was achieved in the Rhodamine B degradation experiment by N doping. The kinetic constant of the N-doped TNT arrays sample was almost twice higher than that of the undoped sample. Further analysis by X-ray photoelectron spectroscopy supported that electrochemical deposition is a simple and efficient method for N doping into TiO2 nanotube arrays.

Porous TiNb24O62 microspheres as high-performance anode materials for lithium-ion batteries of electric vehicles

TiNb24O62 is explored as a new anode material for lithium-ion batteries. Microsized TiNb24O62 particles (M-TiNb24O62) are fabricated through a simple solid-state reaction method and porous TiNb24O62 microspheres (P-TiNb24O62) are synthesized through a facile solvothermal method for the first time. TiNb24O62 exhibits a Wadsley-Roth shear structure with a structural unit composed of a 3 × 4 octahedron-block and a 0.5 tetrahedron at the block-corner. P-TiNb24O62 with an average sphere size of ∼2 μm is constructed by nanoparticles with an average size of ∼100 nm, forming inter-particle pores with a size of ∼8 nm and inter-sphere pores with a size of ∼55 nm. Such desirable porous microspheres are an ideal architecture for enhancing the electrochemical performances by shortening the transport distance of electrons/Li+-ions and increasing the reaction area. Consequently, P-TiNb24O62 presents outstanding electrochemical performances in terms of specific capacity, rate capability and cyclic stability. The reversible capacities of P-TiNb24O62 are, respectively, as large as 296, 277, 261, 245, 222, 202 and 181 mA h g-1 at 0.1, 0.5, 1, 2, 5, 10 and 20 C, which are obviously larger than those of M-TiNb24O62 (258, 226, 210, 191, 166, 147 and 121 mA h g-1). At 10 C, the capacity of P-TiNb24O62 still remains at 183 mA h g-1 over 500 cycles with a decay of only 0.02% per cycle, whereas the corresponding values of M-TiNb24O62 are 119 mA h g-1 and 0.04%. These impressive results indicate that P-TiNb24O62 can be a promising anode material for lithium-ion batteries of electric vehicles.

Porous ZrNb24O62 nanowires with pseudocapacitive behavior achieve high-performance lithium-ion storage

The ever-increasing power and energy demands for modern consumer electronics and electric vehicles are driving the pursuit of energy-storage technologies beyond the current horizon. Pseudocapacitive charge storage is one of the most effective and promising approaches to fill this technology gap, owing to its potential to deliver both high power and energy densities. Typically, titanium niobium oxides (TiNbxO2+2.5x (x = 2, 5 and 24)) with intrinsic pseudocapacitance, high safety and theoretical capacities of 388–402 mA h g−1 are recognized as promising anode materials for lithium-ion batteries. However, their poor conductivity and low Li+-ion diffusion coefficient are known to be the major hurdles limiting the full utilization of their pseudocapacitive effects, leading to their lackluster rate capabilities. Herein, we employ a facile electrospinning method to prepare one-dimensional hierarchically porous ZrNb24O62 nanowires (P-ZrNb24O62) with an ultra-large Li+-ion diffusion coefficient as a new intercalating pseudocapacitive material for boosting Li+-ion storage. The P-ZrNb24O62 exhibits excellent electrochemical performances, including a high reversible capacity (320 mA h g−1 at 0.1C), safe working potential (∼1.67 V vs. Li/Li+), high initial coulombic efficiency (90.1%), outstanding rate capability (182 mA h g−1 at 30C) and durable long-term cyclability (90.2% capacity retention over 1500 cycles).

Metallic Graphene‐Like VSe2 Ultrathin Nanosheets: Superior Potassium‐Ion Storage and Their Working Mechanism

Potassium-ion batteries (KIBs) are receiving increasing interest in grid-scale energy storage owing to the earth abundant and low cost of potassium resources. However, their development still stays at the infancy stage due to the lack of suitable electrode materials with reversible depotassiation/potassiation behavior, resulting in poor rate performance, low capacity, and cycling stability. Herein, the first example of synthesizing single-crystalline metallic graphene-like VSe2 nanosheets for greatly boosting the performance of KIBs in term of capacity, rate capability, and cycling stability is reported. Benefiting from the unique 2D nanostructure, high electron/K+ -ion conductivity, and outstanding pseudocapacitance effects, ultrathin VSe2 nanosheets show a very high reversible capacity of 366 mAh g-1 at 100 mA g-1 , a high rate capability of 169 mAh g-1 at 2000 mA g-1 , and a very low decay of 0.025% per cycle over 500 cycles, which are the best in all the reported anode materials in KIBs. The first-principles calculations reveal that VSe2 nanosheets have large adsorption energy and low diffusion barriers for the intercalation of K+ -ion. Ex situ X-ray diffraction analysis indicates that VSe2 nanosheets undertake a reversible phase evolution by initially proceeding with the K+ -ion insertion within VSe2 layers, followed by the conversion reaction mechanism.

Ni nanobelts induced enhancement of hole transport and collection for high efficiency and ambient stable mesoscopic perovskite solar cells

Highly efficient photo-generated carrier transfer is one of the key factors in determining the performance of organic–inorganic hybrid perovskite solar cells (PSCs). Here, we demonstrate a strategy for improved hole transfer and collection by employing a composite hole transporting material (HTM) consisting of free standing Ni nanobelts dispersed in the widely used 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD). It is found that power conversion efficiency (PCE) and ambient stability of mesoscopic PSCs have been improved. To be more specific, in order to prevent significant charge recombination induced by direct contact of the metal Ni with a perovskite absorber, a spiro-OMeTAD intermediate layer was spin-coated on the CH3NH3PbI3 layer prior to the sequentially deposited layers of Ni nanobelts and spiro-OMeTAD. With this architecture, the optimized PSC achieved a champion PCE of 16.18% with a short-circuit current density (Jsc) of 21.64 mA cm−2, an open-circuit voltage (Voc) of 1.02 V, and a fill factor (FF) of 73.3% under reverse scanning. Despite the small J–V hysteresis, a higher stabilized efficiency up to 14.47% near the maximum power point could be reached for the device fabricated with 1.8 mg mL−1 Ni nanobelts compared with the pristine one (12.05%). However in the presence of highly hygroscopic lithium-bis(trifluoromethane) sulfonimide (Li-TFSI), PSCs in conjunction with Ni nanobelts present an impressively favorable ambient stability with an observed PCE retention rate of over 85% after 4-week storage with exposure to ambient air without any encapsulation.

Morphology and structure characterization of bacterial celluloses produced by different strains in agitated culture

The influence of bacterial species/strains in agitated culture was investigated on the morphology and structure characteristics of bacterial cellulose.

Hollow Si/SiOx nanosphere/nitrogen-doped carbon superstructure with a double shell and void for high-rate and long-life lithium-ion storage

Silicon (Si) is a promising anode candidate for lithium-ion batteries (LIBs) owing to its unprecedented theoretical capacity of 4200 mA h g−1 and earth-abundant supply (26.2 wt%). Nevertheless, the huge volume expansion and unstable solid-electrolyte interface (SEI) of Si in multiple cycles make it very hard to simultaneously achieve high-energy and long-term cycle life for applications in large-scale renewable energy storage. Herein, we demonstrate a new class of Si/SiOx@void@nitrogen-doped carbon double-shelled hollow superstructure (Si/SiOx-DSHS) electrodes that are capable of accommodating huge volume changes without pulverization during cycling. Benefiting from the unique double-shelled hollow superstructure, Si/SiOx-DSHSs can facilitate the formation of a highly stable SEI layer and provide superior kinetics toward Li+-ion storage. The diffusion-controlled process and the capacitance-type reaction can work together to endow Si/SiOx-DSHSs with remarkable electrochemical characteristics, especially at high current density. These important characteristics make Si/SiOx-DSHSs deliver a large reversible capacity (1290 mA h g−1 at 0.1C), high first-cycle coulombic efficiency (71.7%), superior rate capability (360 mA h g−1 at 10C), and excellent cycling behavior up to 1000 cycles with a small capacity decay of 10.2%. The Si/SiOx-DSHSs are among the best Si-based anode materials for LIBs reported to date.

Intercalating Ti2Nb14O39 Anode Materials for Fast-Charging, High-Capacity and Safe Lithium-Ion Batteries

Ti-Nb-O binary oxide materials represent a family of promising intercalating anode materials for lithium-ion batteries. In additional to their excellent capacities (388-402 mAh g-1 ), these materials show excellent safety characteristics, such as an operating potential above the lithium plating voltage and minimal volume change. Herein, this study reports a new member in the Ti-Nb-O family, Ti2 Nb14 O39 , as an advanced anode material. Ti2 Nb14 O39 porous spheres (Ti2 Nb14 O39 -S) exhibit a defective shear ReO3 crystal structure with a large unit cell volume and a large amount of cation vacancies (0.85% vs all cation sites). These morphological and structural characteristics allow for short electron/Li+ -ion transport length and fast Li+ -ion diffusivity. Consequently, the Ti2 Nb14 O39 -S material delivers significant pseudocapacitive behavior and excellent electrochemical performances, including high reversible capacity (326 mAh g-1 at 0.1 C), high first-cycle Coulombic efficiency (87.5%), safe working potential (1.67 V vs Li/Li+ ), outstanding rate capability (223 mAh g-1 at 40 C) and durable cycling stability (only 0.032% capacity loss per cycle over 200 cycles at 10 C). These impressive results clearly demonstrate that Ti2 Nb14 O39 -S can be a promising anode material for fast-charging, high capacity, safe and stable lithium-ion batteries.