Various transition metal oxide-based nanostructures with outstanding lithium-ion storage properties are considered as the most appealing candidates to substitute conventional carbonaceous anode materials in lithium-ion batteries. However, the rational design and tailored synthesis of hybrid materials with specific components, morphologies and structures are crucial to achieving superior electrochemical performances. In this paper, we have designed the synthesis of nanostructured anatase TiO2-modified iron oxides (FexOy) on/among carbon nanotubes (CNTs) (denoted as TFCs) by a simple and inexpensive bottom-up assembly approach. In the as-designed TFCs, TiO2 modifications include two forms: TiO2-coated on FexOy, and TiO2 nanoparticles distributed among TFCs, which play a significant role in avoiding the aggregation and pulverization of the FexOy nanoparticles. With the introduced TiO2 as a buffer material, and the CNTs framework as a porous 3D conducting/buffering network and an effective substrate for anchoring FexOy nanoparticles, as compared to all of the existing analogues reported, the as-designed TFCs display overwhelmingly superior Li+ storage properties, to be specific, good capacity retention with 922 mAh g−1 at 500 mA g−1 and 1089 mAh g−1 at 200 mA g−1, excellent rate capability with current densities varying from 50 mA g−1 to 10 A g−1 and remarkable cycling performance with the capacity increased from 584 to 922 mAh g−1 at 500 mA g−1 over 450 cycles (remaining stable at around 920 mAh g−1 after the 420th cycle) after the rate tests for the same tested cell. We believe that the fascinating TFCs as well as other hybrids with similar structures can be easily extended for diverse applications, such as supercapacitors and catalysts, thus exhibiting broad prospects in the design of high-performance hybrid materials.

On the way to become promising oxygen reduction reaction (ORR) catalysts, the hybrids composed of reduced graphene oxide (RGO) and transition metal oxides are suffering from stacking of RGO sheets. In this work, a Co3O4/RGO/acetylene black (AB) hybrid was successfully synthesized via a facile one-step solution-phase route with sandwiching of AB particles between the RGO sheets during the synthesis of Co3O4/RGO, which can effectively tackle the stacking of RGO sheets. Compared with Co3O4/RGO, Co3O4/RGO/AB-P (mixing AB with the pre-prepared Co3O4/RGO with stirring), Co3O4/RGO/AB-M (mixing AB with Co3O4/RGO during the fabrication of the Co3O4/RGO catalytic layer for ORR) and commercial 10 wt% Pt/C, the Co3O4/RGO/AB hybrid exhibits increases of 50.6%, 32.5%, 37.9% and 8.9% in the ORR current density, respectively. This indicates that the introduction strategy of AB to Co3O4/RGO plays a vital role in the enhancement of ORR catalytic activity. Moreover, the Co3O4/RGO/AB hybrid shows a subtle ascending trend in the ORR current density during continuous operation for 72000 s, while Pt/C exhibits a 9.0% decrease. The exceptional ORR catalytic performance of Co3O4/RGO/AB can also be ascribed to the large specific surface area, well-anchored Co3O4 nanoparticles on the RGO sheets, and low ohmic and kinetic impedances for ORR. We hope this work will be conducive for the extensive commercial applications of fuel cells.

•Anatase-TiO2/CNTs nanocomposite was prepared by a facile and scalable hydrolysis route.•The composite exhibits super-high rate capability and excellent cycling stability for LIBs.•The nanocomposite shows great potential as a superior anode material for LIBs.Anatase-TiO2/carbon nanotubes (CNTs) with robust nanostructure is fabricated via a facile two-step synthesis by ammonia water assisted hydrolysis and subsequent calcination. The as-synthesized nanocomposite was characterized employing X-ray powder diffraction, Fourier transform infrared spectrophotometry, Raman spectrophotometry, thermal gravimetric analysis, transmission electron microscopy, high-resolution transmission electron microscopy and selected area electronic diffraction, and its electrochemical properties as an anode material for lithium-ion batteries (LIBs) were investigated by cyclic voltammetry, galvanostatic discharge/charge test and electrochemical impendence spectroscopy. The results show that the pure anatase TiO2 nanoparticles with diameters of about 10 nm are uniformly distributed on/among the CNTs conducting network. The as-synthesized nanocomposite exhibits remarkably improved performances in LIBs, especially super-high rate capability and excellent cycling stability. Specifically, a reversible capacity as high as 92 mA h g−1 is achieved even at a current density of 10 A g−1 (60 C). After 100 cycles at 0.1 A g−1, it shows good capacity retention of 185 mA h g−1 with an outstanding coulombic efficiency up to 99%. Such superior Li+ storage properties demonstrate the reinforced synergistic effects between the nano-sized TiO2 and the interweaved CNTs network, endowing the nanocomposite with great application potential in high-power LIBs.Graphical abstract

•A well-dispersed Pd/GO nanocomposite was fabricated via a facile one-step chemical reduction method.•This nanocomposite displays excellent comprehensive performances for the electrochemical detection of paracetamol.•This proposed method was successfully applied to detect paracetamol in commercial tablets and human urines.Well-dispersed Pd nanoparticles were facilely anchored on graphene oxide (Pd/GO) via a one-pot chemical reduction of the Pd2+ precursor without any surfactants and templates. The morphology and composition of the Pd/GO nanocomposite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and energy dispersive analysis of X-ray (EDX). The stepwise fabrication process of the Pd/GO modified electrode and its electrochemical sensing performance towards paracetamol was evaluated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The experimental results indicate that the as-synthesized Pd nanoparticles are relatively uniform in size (5–10 nm) without large aggregation and uniformly distributed in the carbon matrix with the overall Pd content of 28.77 wt% in Pd/GO. Compared with the GO modified electrode, the Pd/GO modified electrode shows a better electrocatalytic activity to the oxidation of paracetamol with lower oxidation potential and larger peak current, so the Pd/GO nanocomposite can be used as an enhanced sensing platform for the electrochemical determination of paracetamol. The kinetic parameters of the paracetamol electro-oxidation at Pd/GO electrode were studied in detail, and the determination conditions were optimized. Under the optimal conditions, the oxidation peak current is linear to the paracetamol concentration in the ranges of 0.005–0.5 μM and 0.5–80.0 μM with a detection limit of 2.2 nM. Based on the high sensitivity and good selectivity of the Pd/GO modified electrode, the proposed method was successfully applied to the determination of paracetamol in commercial tablets and human urines, and the satisfactory results confirm the applicability of this sensor in practical analysis.

α-MoO3 nanobelts were successfully prepared by a facile hydrothermal method with sodium molybdate (Na2MoO4) as the Mo source and NaCl as the capping agent. The as-prepared products were characterized using Fourier transformation infrared spectrophotometry (FT-IR), X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and selected area electronic diffraction (SAED) and their pseudocapacitive properties were investigated in a 0.5 M aqueous Li2SO4 solution by cyclic voltammetry (CV), chronopotentiometry (CP) and AC impendence. The results show that the dimensions of the as-prepared α-MoO3 nanobelts are 200–400 nm in width, ca. 60 nm in thickness and 3–8 µm in length. The redox potential for the α-MoO3 nanobelts is found in the range of −0.3 to −1.0 V vs. SCE, which indicates that the α-MoO3 nanobelts can be used as anode electrode materials for hybrid supercapacitors. The specific capacitances of the α-MoO3 nanobelts at 0.1, 0.25, 0.5 and 1 A g−1 are 369, 326, 256 and 207 F g−1, respectively. The maximum specific capacitance of the α-MoO3 nanobelts is much higher than those of MoO3 nanoplates with 280 F g−1, MoO3 nanowires with 110 F g−1 and MoO3 nanorods with 30 F g−1 recently reported in literature. Furthermore, the α-MoO3 nanobelt electrode exhibits a good cycle stability with more than 95% of the initial specific capacitance maintained after 500 cycles. Additionally, the present route to prepare nanostructured MoO3 is much less expensive than those with Mo powders as the Mo source. Overall, the obtained high performance α-MoO3 nanobelts could be a promising electrode material for supercapacitors.

•The Li3V2(PO4)3 particles coated by a ∼8 nm thin layer carbon was prepared through a carbon thermal reduction route.•The activated carbon//carbon-coated Li3V2(PO4)3 asymmetric hybrid capacitor was fabricated.•The asymmetric hybrid capacitor exhibits good electrochemical properties.The electrochemical performance of the carbon-coated Li3V2(PO4)3 (LVP/C) composite prepared through a carbon thermal reduction route has been investigated. The results show that the LVP/C composite exhibits reversible Li+ de-intercalating/intercalating behaviors with the swing potential in the range of −0.2 to 0.8 V vs. SCE in a neutral Li2SO4 aqueous solution. It has also been found that the activated carbon (AC)//LVP/C asymmetric hybrid capacitor exhibits good electrochemical properties. The asymmetric hybrid capacitor shows sloping profiles in the galvanostatic charge–discharge curves with the operating voltage in the range of 0–1.7 V and can work steadily. Both of the capacity retention and coulombic efficiency of the asymmetric hybrid capacitor can retain more than 90% after 1000 charge–discharge cycles at a current density of 250 mA g−1. At the power density of 102 W kg−1, the energy density of the asymmetric hybrid capacitor is 35 Wh kg−1, and even at 2000 W kg−1, the energy density can achieve 5 Wh kg−1. In addition, we have found that the conductive additive such as acetylene black is not required during the electrode fabricating process with the LVP/C composite as an electrode material, and this will serve the interest of saving cost. This work could provide an evidence for the development of aqueous asymmetric hybrid capacitors using LVP/C as electrode materials.

•A novel RGO–Cu2O–TiO2 was fabricated via a facile one-step solution-phase route.•The ternary nanocomposite displays excellent cycling stability for supercapacitors.•The introduction of TiO2 to RGO–Cu2O can markedly improve supercapacitor properties.A novel reduced graphene oxide (RGO)–Cu2O–TiO2 ternary nanocomposite was successfully fabricated via a facile one-step solution-phase method. The synthesized RGO–Cu2O–TiO2 nanocomposite was characterized by X-ray powder diffraction, transmission electron microscopy, atomic force microscopy and Raman spectroscopy, and its electrochemical properties as an active electrode material for supercapacitors were investigated through cyclic voltammetry (CV) and galvanostatic charge/discharge measurements in a 6 M KOH aqueous electrolyte. The obtained RGO–Cu2O–TiO2 nanocomposite exhibits a specific capacitance of 80 F g−1 at a current density of 0.2 A g−1 in the 6 M KOH electrolyte, nearly twice the value of 41.4 F g−1 for the RGO–Cu2O nanocomposite and 2.5 times the value of 32.7 F g−1 for the RGO–TiO2 nanocomposite. Furthermore, the specific capacitance of RGO–Cu2O–TiO2 increases from 80 to 91.5 F g−1 after 1000 cycles, which can be said the least that the capacitance has not changed within error, while the specific capacitances of RGO–Cu2O and RGO–TiO2 decrease from 41.4 to 34.5 F g−1 and from 32.7 to 25.2 F g−1, respectively.Graphical abstract

A three-dimensional (3D) reduced graphene oxide (rGO)/multi-walled carbon nanotubes (MWCNTs)/Fe2O3 ternary composite was fabricated by a facile, green and economical one-step urea-assisted hydrothermal approach as a promising anode material for high-performance lithium ion batteries. Designing and tailoring the 3D porous hierarchical nanostructure of rGO/MWCNTs/Fe2O3 contributes to a robust hybrid material with overwhelmingly superior electrochemical performances compared with bare Fe2O3, MWCNTs/Fe2O3, rGO/Fe2O3 and a physical mixture of rGO/Fe2O3 and MWCNTs, due to the strong synergistic effects among the individual component. The 3D rGO/MWCNTs/Fe2O3 composite exhibits highly enhanced specific capacity, cycling performance and rate capability: initial discharge and charge capacities of 1692 and 1322 mAh g−1 at 100 mA g−1, respectively, 1118 mAh g−1 after 50 cycles at 100 mA g−1 and 785 mAh g−1 at 1000 mA g−1. The assembling mechanism well illustrates the simple strategy, and the comprehensive electrochemical investigations further demonstrate its supernormal effectiveness, which could be extended to various transition metal oxides for energy storage and conversion.

α-MoO3 nanobelts were successfully prepared by a facile hydrothermal method with sodium molybdate (Na2MoO4) as the Mo source and NaCl as the capping agent. The as-prepared products were characterized using Fourier transformation infrared spectrophotometry (FT-IR), X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and selected area electronic diffraction (SAED) and their pseudocapacitive properties were investigated in a 0.5 M aqueous Li2SO4 solution by cyclic voltammetry (CV), chronopotentiometry (CP) and AC impendence. The results show that the dimensions of the as-prepared α-MoO3 nanobelts are 200–400 nm in width, ca. 60 nm in thickness and 3–8 µm in length. The redox potential for the α-MoO3 nanobelts is found in the range of −0.3 to −1.0 V vs. SCE, which indicates that the α-MoO3 nanobelts can be used as anode electrode materials for hybrid supercapacitors. The specific capacitances of the α-MoO3 nanobelts at 0.1, 0.25, 0.5 and 1 A g−1 are 369, 326, 256 and 207 F g−1, respectively. The maximum specific capacitance of the α-MoO3 nanobelts is much higher than those of MoO3 nanoplates with 280 F g−1, MoO3 nanowires with 110 F g−1 and MoO3 nanorods with 30 F g−1 recently reported in literature. Furthermore, the α-MoO3 nanobelt electrode exhibits a good cycle stability with more than 95% of the initial specific capacitance maintained after 500 cycles. Additionally, the present route to prepare nanostructured MoO3 is much less expensive than those with Mo powders as the Mo source. Overall, the obtained high performance α-MoO3 nanobelts could be a promising electrode material for supercapacitors.

Various transition metal oxide-based nanostructures with outstanding lithium-ion storage properties are considered as the most appealing candidates to substitute conventional carbonaceous anode materials in lithium-ion batteries. However, the rational design and tailored synthesis of hybrid materials with specific components, morphologies and structures are crucial to achieving superior electrochemical performances. In this paper, we have designed the synthesis of nanostructured anatase TiO2-modified iron oxides (FexOy) on/among carbon nanotubes (CNTs) (denoted as TFCs) by a simple and inexpensive bottom-up assembly approach. In the as-designed TFCs, TiO2 modifications include two forms: TiO2-coated on FexOy, and TiO2 nanoparticles distributed among TFCs, which play a significant role in avoiding the aggregation and pulverization of the FexOy nanoparticles. With the introduced TiO2 as a buffer material, and the CNTs framework as a porous 3D conducting/buffering network and an effective substrate for anchoring FexOy nanoparticles, as compared to all of the existing analogues reported, the as-designed TFCs display overwhelmingly superior Li+ storage properties, to be specific, good capacity retention with 922 mAh g−1 at 500 mA g−1 and 1089 mAh g−1 at 200 mA g−1, excellent rate capability with current densities varying from 50 mA g−1 to 10 A g−1 and remarkable cycling performance with the capacity increased from 584 to 922 mAh g−1 at 500 mA g−1 over 450 cycles (remaining stable at around 920 mAh g−1 after the 420th cycle) after the rate tests for the same tested cell. We believe that the fascinating TFCs as well as other hybrids with similar structures can be easily extended for diverse applications, such as supercapacitors and catalysts, thus exhibiting broad prospects in the design of high-performance hybrid materials.