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A facile strategy of electrophoretic deposition has been employed to fabricate a thin film photoelectrochemical (PEC) sensor of functionalized N–doped graphene quantum dots (F–NGQDs) embedded in BiOBr nanosheets, which were prepared by a two–step hydrothermal method, loaded onto indium–tin–oxide coated glass substrate (F–NGQDs/BiOBr/ITO). Electrophoretic deposition provides a mild and environmentally friendly method for PEC film formation. Multiple techniques were applied to investigate the electronic, optical properties and structure of F–NGQDs/BiOBr thin films photoelectrodes. It was found that F–NGQDs/BiOBr thin films with NGQDs/BiOBr heterojunction possess an enhanced charge transfer and absorption wavelengths under visible light, particularly when compared to pristine F–BiOBr films, thus producing an increase in the observed photocurrent. Sensing performance measurements showed the F–NGQDs/BiOBr/ITO photoelectrode has a higher photoelectric response current to paracetamol, it was used to detect trace paracetamol under visible light irradiation. The sensor exhibited a wide linear range, low detection limit and good sensitivity, given the photoactivity of NGQDs/BiOBr heterojunction. The developed PEC sensor displayed an acute response to paracetamol in a linear range of 0.01 μM–20.0 μM with a detection limit of 3.33 nM, under optimal conditions. Here we present evidence that F–NGQDs/BiOBr/ITO photoelectrode is a promising candidate for PEC analysis. • NGQDs embedded in BiOBr nanosheets were prepared by a two-step hydrothermal method. • F–NGQDs/BiOBr nanocomposites were deposited onto ITO coated glass substrate by electrophoretic deposition. • This platform is simple in preparation and has the potential to achieve simple and specific detection of paracetamol. [ABSTRACT FROM AUTHOR]

Abstract In terms of the unique features of good suspensibility in water, superior absorbability, adhensivity, cation exchangeability and rapid ion diffusion channels, lithium magnesium silicate (LMSO) might be an appropriate modifier for Li 4 Ti 5 O 12 (LTO) by simply forming coating on LTO particles. According to a series of comparative experiments performed under various conditions, when the mixture of LTO and LMSO was roasted at 700 °C to form LMSO-coated LTO, the rate properties were significantly boosted (attaining cycling capacities of 160.2, 157.8, 155.8, 151.3 and 145.5 mAh g−1 with multiplying current density from 0.1 to 1.6 A g−1). Upon cycling at 0.5 A g−1 for 900 cycles, a capacity of 140.6 mAh g−1 was maintained. Compared to the pristine LTO, the markedly boosted rate properties and cyclability are ascribed to the LMSO coating for suppressing grain aggregation and growth, the optimized Li+ and electron transfer in electrolyte by interacting with LMSO, the enhanced electronic conductivity of LTO resulted from superficial co-doping of Mg2+ and Si4+, the meliorated ionic conductivity associating with the Li+ diffusion channels and cation exchangeability of LMSO, as well as the diminished polarization after the modification by LMSO. [ABSTRACT FROM AUTHOR]

Spinel Li 4 Ti 5 O 12 co-doped with Mg 2+ and F − was synthesized by solid-state reaction of anatase TiO 2 , Li 2 CO 3 , NH 4 F, and Mg(NO 3 ) 2 . For comparison, Mg 2+ -doped and F − -doped Li 4 Ti 5 O 12 were prepared using the same method. The structure and electrochemical performance of the prepared materials were investigated by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, electrochemical impedance spectroscopy, and galvanostatic charge-discharge tests. Using an internal standard and Rietveld refinement, we calculated the lattice parameters of the samples. After co-doping with Mg 2+ and F − , the dopant ions enter the Li 4 Ti 5 O 12 lattice, resulting in the reduction of Ti 4+ to Ti 3+ , and increasing the conductivity of the material. Furthermore, the Mg 2+ and F − co-doping technique resulted in smaller primary particles with a narrow size distribution, factors that can accelerate transfer of Li + between the electrode and electrolyte. Consequently, the Mg 2+ and F − co-doped Li 4 Ti 5 O 12 material exhibits a superior rate performance and delivers discharge capacities of 159.4, 154.1, 146.5, 120.8, 102.7, and 76 mAh g −1 at 0.2C, 0.5C, 1C, 3C, 5C, and 10C, respectively, significantly higher than those of pure Li 4 Ti 5 O 12 (155.4, 138.6, 124.2, 94.1, 76.7, and 52.2 mAh g −1 at the same C-rates). Moreover, the Mg 2+ and F − co-doped Li 4 Ti 5 O 12 showed outstanding cycling stability, and the capacity retention was 99.62% after 150 cycles at 5C rate. Therefore, the Mg 2+ and F − co-doping technique has proven an effective approach to improve the electrochemical performance of Li 4 Ti 5 O 12 . [ABSTRACT FROM AUTHOR]

Fe 3 O 4 has been regarded as one of the sustainable alternatives for anode materials of Li-ion batteries (LIBs), but the severe volume expansion and agglomeration of Fe 3 O 4 nanoparticles pose limitations to the lithium storage capability. In this paper, Fe 3 O 4 nanoparticles are loaded on the carbon derived from inner pomelo pericarp to form Fe 3 O 4 /C composite. Benefiting from the synergistic effect of the good electronic conductivity of the biochar and the high capacity of Fe 3 O 4 nanoparticles, the composite delivers a pronounced reversible capacity of 1003.3 mAh g −1 after 200 cycles at 100 mA g −1 , and reveals an impressive high rate capacity of 634.6 mAh g −1 at 500 mA g −1 with the capacity fading of 0.074% per cycle, suggesting the great potential as anode materials for LIBs. The mineral substances of uniformly distributed KCl and CaCO 3 in the biochar play an important role in enhancing the electrochemical performance of the composite. [ABSTRACT FROM AUTHOR]

In this paper, three dimensional reduced graphene oxide skeleton onto nickel foam (3D RGO NF) was fabricated by a facile dip-coating method combined with alkaline reduction. The as-prepared skeleton was used as a substrate to immobilize Ni-Co layered double hydroxide (Ni-Co LDH) with special morphology of nanowires to effectively prevent the agglomeration of material. The Ni-Co LDH/3D RGO NF electrode exhibited an enhanced specific capacitance of 1054 F g −1 compared with Ni-Co LDH/NF, excellent rate capability (60% capacitance retention with a ten-fold increase in current density) as well as long cyclic life (95% capacity retention after 2000 cycles). In addition, an aqueous asymmetric supercapacitor was composed of Ni-Co LDH/3D RGO NF as positive electrode and activated carbon as negative electrode, which exhibited a specific capacitance of 108.7 F g −1 at 2 mA cm −2 in a potential range from 0 to 1.6 V; it showed maximum energy density of 38.6 Wh kg −1 at 69.5 W kg −1 . Moreover, the Ni-Co LDH/3D RGO NF//AC has an outstanding cycling stability (about 70% capacitance retention after 4000 cycles), which makes it a potential candidate for electrochemical energy storage devices. [ABSTRACT FROM AUTHOR]

Commercial TiO 2 usually exhibits poor electrochemical performance for Li-ion batteries. In this work, we fabricated the carbon-coated commercial TiO 2 with soft carbon at 750 °C using pitch as the carbon source. The carbon-coated products reveal markedly enhanced capacity, excellent cyclability at a current density of 500 mA g −1 . The enhanced performance associates with the improved electronic and ionic conductivities results from the pitch-derived carbon with high graphitization degree as well as interfacial Li-ion storage. [ABSTRACT FROM AUTHOR]

Nitrogen-doped TiO 2 nanoparticles coated with N-doped carbon are prepared by simply hydrolyzing tetrabutyl titanate to obtain TiO 2 nanoparticles followed by heating the mixture of nanoparticles and urea at 550 °C for 5 h. The combination of simultaneously N-doping with coating carbon results in the enhancement in electronic and ionic conductivities, thus the modified TiO 2 exhibits outstanding reversible capacities of 227.7, 204.0, 186.4, 160.6, 113.1 mAh g −1 corresponding to current densities of 100, 200, 400, 800 and 1600 mA g −1 . In particular, the modified TiO 2 could deliver an excellent long-term cycling capacity of 106.4 mAh g −1 even cycled 2500 times at a high density of 500 mA g −1 with an average capacity loss of only 0.016% per cycle. The modified TiO 2 fabricated by this simple and economical method could serve as the anode material for lithium-ion batteries with high power-density. [ABSTRACT FROM AUTHOR]

TiO 2 /C nanocomposites were fabricated by simple hydrolysis of tetrabutyl titanate to yield TiO 2 nanoparticles followed by carbonizing the mixture of glucose and TiO 2 at 600 °C. By merely varying the weight ratio of glucose:TiO 2 , the electrochemical performance of the composites could be optimized significantly. At a ratio of 0.8, the composite exhibits a high reversible capacity of 283.7 mA h g −1 after cycling 100 times at a current density of 100 mA g −1 , as well as the capacities of 245.1, 213.6, 179.9 and 136.6 mA h g −1 at the corresponding densities of 200, 400, 800 and 1600 mA g −1 . After cycling 1000 times at 500 mA g −1 , a capacity of 122.8 mA h g −1 was retained for the composite with a ratio of 0.8, and even a capacity of 149.1 mA h g −1 for the composite with a ratio of 0.7. The enhanced performance is ascribed to the carbon-coated TiO 2 nanoparticles uniformly embedding in the carbon matrix with appropriate carbon content. [ABSTRACT FROM AUTHOR]

Cu-modified Li 4 Ti 5 O 12 (LTO) with various Cu-doping contents was prepared via simple hydrolysis of tetrabutyl titanate in the water solution of LiOH · H 2 O and Cu(NO 3 ) 2 · 3H 2 O, followed by sintering the dried mixture at 600 °C for 5 h. By virtue of the slightly increased lattice constant, refined grains with relatively large surface area, improved electronic and ionic conductivities, the modified products exhibit excellent long-term cycling stability at a high current rate of 10 C and outstanding rate performance at 0.1–40 C. Particularly, the product with a Cu-doping content of 0.08 demonstrates prominent long-term cycling performance up to 2500 cycles at 10 C and superior capacity retention even at 10–40 C. The Cu-modified LTO could be used as efficient anode materials for long-life and high-rate lithium ion batteries. [ABSTRACT FROM AUTHOR]

Abstract Among various carbon materials, nitrogen doped single walled carbon nanohorns (N-SWCNHs) have a unique structure of clustered conical cages (2–5 nm in diameter and 40–50 nm in length) arranged in dahlia, bud and seed-like configurations. Each conical cage has five pentagons at their tips which act as potential reactive site with their own distinct chemistry. We exploited these reactive sites of N-SWCNHs by preferentially growing germanium nanocrystals (Ge NCs) onto their conical tips using oleylamine as a mild reducing agent. Therefore, Ge decorated N-SWCNHs (Ge@N-SWCNHs) composite was used, for the first time, as active anode material for lithium ion batteries providing high and stable capacity of 1285 mAh/g at 0.1C after 100 cycles. Our results show that preferential growth of Ge Nanocrystals (NCs) on the tips of N-SWCNHs not only allows high utilization of active material but prevents the aggregation of Ge NCs after multiple cycling. Finally, we highlight the potential role of N-SWCNHs as cheap and industrially scalable conductive host for next generation lithium ion batteries. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have aroused extensive concern in recent years due to their attractive energy storage and conversion efficiency. However, the energy conversion efficiency was largely restricted by the sluggish kinetics and the high cost of the catalysts. In this regard, developing non-precious metal materials as low-cost, highly efficient, and durable catalysts is extremely urgent topic. In this work, Mn doping of cobalt oxynitride (Co 1-x Mn x ON) coupled with nitrogen-doped reduced graphene oxide (N-rGO) nanosheets hybrids was created as a bifunctional and highly efficient catalyst toward the ORR and OER. The electrochemical tests indicated that the catalytic performance for the CoMnON/N-rGO has been greatly improved after Mn and N doping. For ORR, the onset potential and half-wave potential are 0.91 V and 0.83 V, respectively. Meanwhile, it manifests a low overpotential of 350 mV at 10 mA cm −2 , Tafel slope of 70 mV dec −1 in 1.0 M KOH solution towards OER. The charge transfer rate and specific surface area for the hybrid catalyst dramatically increase with the incorporation of Mn and N. Our work provides a new strategy for developing highly efficient and durable electrocatalysts. [ABSTRACT FROM AUTHOR]

The Br− modified LiNi 0.815 Co 0.15 Al 0.035 O 2 (NCA) cathode materials areprepared via a situ doping method for the first time. The structural and electrochemical properties within Br− modified NCA cathode material are in an in-depth analysis. X-ray diffraction (XRD) results show enlarged interslab spacing due to the fact that partial Br− has doped into the bulk particles of NCA to replace O2− in 6c site. Density functional theory (DFT) calculations suggest that Br− doping mainly occurs in the surface layer. Moreover, the Br‒ modified NCA cathode materials present smaller primary particles than pure NCA, which is proved by calculations of particle size from random scanning electron microscopy (SEM) images. X-ray photoelectron spectroscopy (XPS) results certify that the the valence state of Ni3+ is partly reduced to Ni2+ and residual lithium acts as stable LiBr instead of unstable Li 2 CO 3 at the surface of Br‒ modified NCA cathode materials. From the electrochemical tests, 0.2 mol% Br− modified NCA with reduced potential polarization, decreasing value of R sf + R ct and increasing Li+ diffusion coefficient, exhibits excellent cycling performance, even at elevated temperature. These results clearly indicate that Br− modification contributes to the remarkable enhancement of structure stability and cycling performance of NCA. [ABSTRACT FROM AUTHOR]

Abstract As electrode materials for supercapacitors, nanostructured hybrids always show better performance compared to corresponding single material. In this work, Ni(OH) 2 flakes/MnO 2 nanosheets hybrid hierarchical architecture (Ni(OH) 2 /MnO 2 HHA) was constructed on Ni foam (NF) through a two-step hydrothermal reaction. Interestingly, MnO 2 nanosheets are vertically grown on the both sides of Ni(OH) 2 flakes, forming a highly porous structure with large specific surface area and amounts of diffusion channels. As a binder-free electrode for supercapacitors, Ni(OH) 2 /MnO 2 HHA/NF exhibits a high specific capacity of 253.6 mAh g−1 at 2 A g−1, which is much higher than the individual Ni(OH) 2 and MnO 2. The excellent electrochemical performance can be attributed to the highly porous architecture, two-dimensional (2D) feature and synergistic effect between Ni(OH) 2 and MnO 2. The asymmetric hybrid supercapacitor was assembled using Ni(OH) 2 /MnO 2 HHA/NF (24 h) as positive electrode and activated carbon (AC) as negative electrode in 3 M KOH. The hybrid supercapacitor cell can be cycled in the voltage window of 0–1.9 V and exhibits a maximum specific energy of 29.9 Wh kg−1 at 1900 W kg−1. The results indicate that the Ni(OH) 2 /MnO 2 HHA/NF electrode shows great potential in design of high-performance energy storage devices. The construction of this 2D branched hierarchical architecture provides an effective method to obtain excellent electrode materials for energy storage. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Despite the low price of commercial TiO 2 (c-TiO 2 ), the poor electrochemical performance restricts its practical application in Li-ion batteries, so clarifying the reasons and taking appropriate measures to improve the performance are of great significance. Herein, c-TiO 2 was coated with carbon at 600 and 750 °C using glucose as the carbon source. The product obtained at 750 °C exhibits markedly enhanced reversible capacities and outstanding rate performance compared to that obtained at 600 °C. In terms of the comparative experiments and detailed characterizations by several techniques, the SO 4 2− remained in the c-TiO 2 is the dominant impurity affecting the electrochemical performance mostly. The thorough decomposition of SO 4 2− at 750 °C and the formation of carbon coating give rise to the enhanced electronic and ionic conductivities of the c-TiO 2 , and thus are responsible for the significant improvement in the electrochemical performance. The easy fabrication and the low cost of the raw materials enable the carbon-coated c-TiO 2 to industrially apply in the LIBs. [ABSTRACT FROM AUTHOR]

• Zn 0.33 Co 0.67 P displays a maximum specific capacitance of 2115.5 F g-1 at 1 A g-1. • Zn-Co phosphide porous nanosheets battery-type advanced material derived from Metal-organic-frameworks is synthesized. • The cycling performance of Zn 0.33 Co 0.67 P electrode has an excellent capacitance retention of 80.4% after 7000 cycles at current density of 10 A g-1. • Zn 0.33 Co 0.67 P//Bi 2 O 3 alkaline SC delivers a high energy density of 83.05 Wh kg-1 at 775.02 W kg-1. Excellent electrode materials are often desired to improve the overall performance of supercapacitors and conversion components, especially electrode materials synthesized by anion replacement to achieve high electrochemical performance. Herein, a zinc–cobalt phosphide electrode material with excellent electrical conductivity is synthesized through a metal–organic framework (MOF)-derived method, followed by phosphating in a tube furnace. As a result, an exchange of phosphorus ions and oxygen ions occurs, yielding a high specific capacitance of 2115.5 F g-1 at 1 A g-1, as well as a superior rate capacity of 1086.5 F g-1 at 50 A g-1. After 7000 cycle tests, 80.3% of the initial specific capacitance is maintained. Phosphorus substitution leads to a narrowed band gap, resulting in outstanding electrical conductivity, as confirmed through density functional theory (DFT) calculations. Subsequently, the self-assembled Zn 0.33 Co 0.67 P//Bi 2 O 3 alkaline supercapacitor exhibits a high energy density of 83.05 Wh kg-1 (248.9 F g-1 at 1 A g-1) at a power density of 775.02 W kg-1. Meanwhile, a capacitance retention of 84.6% after 8000 cycles at a current density of 5 A g-1 is obtained. The outstanding performances of the electrode material in terms of electrical conductivity and electrochemical activity provide a new method for the design of high energy density alkaline supercapacitors (SCs). Image, graphical abstract [ABSTRACT FROM AUTHOR]

Mg2+/F− co-doped LiNi 0.5 Mn 1.5 O 4 cathode material was synthesized by a facile one-step solid-state process. The effect of Mg2+/F− co-doping on grain morphology, phase structure, and electrochemical properties was studied by a series of characterizations. Scanning-electron-microscopy images show that Mg2+/F− co-doped LiNi 0.5 Mn 1.5 O 4 (denoted LNMO-MF) particles grow larger than pure LiNi 0.5 Mn 1.5 O 4 particles. X-ray diffraction, Raman spectra, Fourier transformation infrared spectroscopy, X-ray photoelectron spectroscopy, and cyclic-voltammetry tests indicate that all samples mainly display a Fd -3m space group and more Mn3+ ions in the LNMO-MF sample after Mg2+/F− co-doping, which is conducive to increasing the cationic disorder degree and enhancing the electronic conductivity of electrode material. Results show that the LNMO-MF cathode material delivers an excellent rate performance with discharge capacities of 142, 144, 140 136, 132, 124, 115, and 100 mAh g−1 at 0.2, 0.5, 1, 2, 3, 5, 7, and 10C (1C = 140 mAh g−1), respectively. Remarkably, LNMO-MF also shows cycling stability with a capacity retention of 86.2% at 5C after 400 cycles, which is much higher than that of pure LiNi 0.5 Mn 1.5 O 4 (67.7%). The improvement of LNMO-MF's electrochemical properties could be ascribed to the Mg2+/F− co-doping, delivering a more stable structure, better crystallinity, the highest Li+ diffusion coefficient, and the lowest charge-transfer resistance. [ABSTRACT FROM AUTHOR]