Carbon-coated TiO2 Research Articles

Improving the Li-ion storage performance of commercial TiO2 by coating with soft carbon derived from pitch

Commercial TiO2 usually exhibits poor electrochemical performance for Li-ion batteries. In this work, we fabricated the carbon-coated commercial TiO2 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 500mAg−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.

2D sandwich-like carbon-coated ultrathin TiO2@defect-rich MoS2 hybrid nanosheets: Synergistic-effect-promoted electrochemical performance for lithium ion batteries

Poor cycling performance and rate capability are the major barriers to the application of layered transition-metal sulfide as the next generation anodes materials for lithium-ion batteries (LIBs). In this paper, a smart composite consisting of defect-rich MoS2/carbon-coated ultrathin TiO2/defect-rich MoS2 sandwich-like nanosheets has been constructed to enhance the cycling and rate performances of MoS2. In this uniform sandwich-like structure, carbon-coated ultrathin TiO2 is conformably embedded by defect-rich MoS2 shells via intimate interfacial contacts, while the carbon coats TiO2via Ti–O–C bonds. It is first revealed that the synergistic effect between rich defect in few-layer MoS2 nanosheets and abundant interfaces in the composites, as well as the high structure stability of TiO2 during discharge and charge process, results in excellent performance of the composites as LIBs anode materials. These LIBs anodes achieve the best rate capability (785.9, 507.6 and 792.3mAhg−1 at 0.1, 2 and 0.1Ag−1, respectively) and cycling performance (805.3mAhg−1 at 0.1Ag−1 after 100 cycles) among the TiO2 supported MoS2 based composites reported previous. The synergistic strategy can be expected to benefit the rational design of other anode materials for high-performance LIBs.

Advanced High-Voltage Aqueous Lithium-Ion Battery Enabled by "Water-in-Bisalt" Electrolyte.

A new super-concentrated aqueous electrolyte is proposed by introducing a second lithium salt. The resultant ultra-high concentration of 28 m led to more effective formation of a protective interphase on the anode along with further suppression of water activities at both anode and cathode surfaces. The improved electrochemical stability allows the use of TiO2 as the anode material, and a 2.5 V aqueous Li-ion cell based on LiMn2 O4 and carbon-coated TiO2 delivered the unprecedented energy density of 100 Wh kg(-1) for rechargeable aqueous Li-ion cells, along with excellent cycling stability and high coulombic efficiency. It has been demonstrated that the introduction of a second salts into the "water-in-salt" electrolyte further pushed the energy densities of aqueous Li-ion cells closer to those of the state-of-the-art Li-ion batteries.

Investigation of the electrochemical features of carbon-coated TiO2 anode for application in lithium-ion battery using high voltage LiNi0.5Mn1.5O4 spinel cathode

In this paper we propose a carbon-coated, nano-sized TiO2 anode for application in lithium-ion batteries. The lithiation-delithiation process characteristic of this mixed anatase/rutile material has been investigated in detail, in order to define the optimal operating voltage range and to further enhance the electrode cycle life. Ex-situ x-ray diffraction measurements demonstrate that the rutile phase becomes electrochemically inactive toward lithium intercalation after the first cycle and remains inactive by cycles. The TiO2 electrochemical behavior is studied by means of various techniques, including galvanostatic cycling and potentiodynamic cycling with galvanostatic acceleration. We show that the combination of the TiO2 anode with a high-voltage, LiNi0.5Mn1.5O4 spinel cathode results in an advanced li-ion battery able to exchange reversibly a capacity higher than 100 mAh/g for over 70 cycles at the high rate of 1C. Considering an average working voltage of about 2.9V, the theoretical energy content of the cell here disclosed is about 300 Wh kg−1. Taking into account the energy content and high safety level of the full cell, due to the use of a TiO2-based electrode, by operating at a voltage value well far from the one associated to the common electrolyte decomposition, i.e. about 1.7V, we may propose the anode here studied as suitable material for advanced energy storage systems.

Design and synthesis of ternary Co3O4/carbon coated TiO2 hybrid nanocomposites for asymmetric supercapacitors.

Recently, attention has been focused on the synthesis and application of nanocomposites for supercapacitors, which can have superior electrochemical performance than single structured materials. Here, we report a carbon-coated TiO2/Co3O4 ternary hybrid nanocomposite (TiO2@C/Co) electrode for supercapacitors. A carbon layer was directly introduced onto the TiO2 surface via thermal vapor deposition. The carbon layer provides anchoring sites for the deposition of Co3O4, which was introduced onto the carbon-coated TiO2 surface by hydrazine and the thermal oxidation method. The TiO2@C/Co electrode exhibits much higher charge storage capacity relative to pristine TiO2, carbon-coated TiO2, and pristine Co3O4, showing a specific capacitance of 392.4 F g(-1) at a scan rate of 5 mV s(-1) with 76.2% rate performance from 5 to 500 mV s(-1) in 1 M KOH aqueous solution electrolyte. This outstanding electrochemical performance can be attributed to the high conductivity and high pseudo-capacitive contributions of the nanoscale particles. To evaluate the capacitive performance of a supercapacitor device employing the TiO2@C/Co electrode, we have successfully assembled TiO2@C/Co//activated carbon (AC) asymmetric supercapacitors. The optimized TiO2@C/Co//AC supercapacitor could be cycled reversibly in the voltage range from 0 to 1.5 V, and it exhibits a specific capacitance of 59.35 F g(-1) at a scan rate of 5 mV s(-1) with a specific capacitance loss of 15.4% after 5000 charge-discharge cycles. These encouraging results show great potential in terms of developing high-capacitive energy storage devices for practical applications.

Nano-Sn doped carbon-coated rutile TiO2spheres as a high capacity anode for Li-ion battery

Nano-Sn doped carbon-coated rutile TiO2spheres (C-NS/TiO2-1 and C-NS/TiO2-2) as an improved TiO2-based anode for Li-ion batteries werein situfabricated.

Enhancing Electrochemical Performances of TiO2 Porous Microspheres through Hybridizing with FeTiO3 and Nanocarbon

The carbon-coated TiO2 (TiO2@C) and FeTiO3 (TiO2/FeTiO3@C) hybrid porous microspheres with a specific surface area of 35.1 m2g−1 have been successfully synthesized by carbonizing the mixture of pyrrole with lab-made TiO2/Fe2O3 porous microspheres. The as-prepared TiO2/FeTiO3@C porous electrode material possessed a reversible capacity of 441.5 mAh g−1 after 300 cycles at a current density of 100mAg−1 and a coulombic efficiency of 99%. Comparing with TiO2, TiO2@C, and TiO2/Fe2O3 porous microspheres, the TiO2/FeTiO3@C porous composites exhibited superior cycling and rate performances, which are rooted in the synergistic effect that generated by little volume variation of TiO2 matrix, high capacity of FeTiO3 and good electrical conductivity of carbon coating (with a thickness of 2–5nm deposited on the surface and inner wall of pores) during the charge/discharge processes.

Enhanced electrochemical performance of carbon-coated TiO2 nanobarbed fibers as anode material for lithium-ion batteries

Abstract We report the electrochemical performance of carbon-coated TiO 2 nanobarbed fibers (TiO 2 @C NBFs) as anode material for lithium-ion batteries. The TiO 2 @C NBFs are composed of TiO 2 nanorods grown on TiO 2 nanofibers as a core, coated with a carbon shell. These nanostructures form a conductive network showing high capacity and C-rate performance due to fast lithium-ion diffusion and effective electron transfer. The TiO 2 @C NBFs show a specific reversible capacity of approximately 170 mAh g − 1 after 200 cycles at a 0.5 A g − 1 current density, and exhibit a discharge rate capability of 4 A g − 1 while retaining a capacity of about 70 mAh g − 1 . The uniformly coated amorphous carbon layer plays an important role to improve the electrical conductivity during the lithiation–delithiation process.

Assembling porous carbon-coated TiO2(B)/anatase nanosheets on reduced graphene oxide for high performance lithium-ion batteries

Novel porous carbon-coated mixed-phase porous TiO2 (TiO2(B)/anatase) nanosheets/reduced graphene oxide composites (TiO2@C/RGO) are successfully prepared through a facile one-pot solvothermal process followed by subsequent heat treatment in H2/Ar. The as-formed composites have a hierarchical porous structure, involving an average pore size of 28.56nm, a large pore volume of 0.589cm3g−1 and a desired surface area (136.19m2g−1). When used as an anode material in LIBs, TiO2@C/RGO exhibits stable cycling performance with a reversible capacity of 272.9mAhg−1 (with the second capacity retention of 151.1%) after 500 cycles at a current density of 100mAg−1, much higher than that of TiO2@C (177.6mAhg−1, 123.9% of the discharge capacity in second cycle) and TiO2 (75.1mAhg−1, corresponding to 96.5% of the original capacity). More impressively, the capacity of TiO2@C/RGO can reach 158.6mAhg−1 after 500 cycles even at 800mAg−1 with Coulombic efficiency above 99.0%. The superior electrochemical performance of TiO2@C/RGO may be attributed to its unique 3D hierarchical porous structures, the existence of carbon, large surface area and extremely reduced diffusion length.

Carbon-Coated Mesoporous TiO2 Nanocrystals Grown on Graphene for Lithium-Ion Batteries.

Graphene-based hybrids have been well studied as advanced catalysts and high-performance electrode materials. In this Article, we have fabricated a novel graphene@mesoporous TiO2 nanocrystals@carbon nanosheet by a simple one-step solvothermal method. We have found that titanocene dichloride can act as an extraordinary source with multiple roles for forming TiO2 nanocrystals, ultrathin carbon outer shells, and cross-linkers to binding TiO2 nanocrystals on graphene surface. Moreover, it also serves as a controlling agent to produce mesoporous structure on TiO2 nanocrystals. The loading-concentration of mesoporous TiO2 nanocrystals on graphene sheets can be well controlled by adjusting the initial content of titanocene dichloride. The as-obtained graphene@mTiO2@carbon nanosheets possess a uniform sandwich-like structure, highly crystalline mesoporous TiO2 nanocrystals, a high surface area of ∼209 m(2)/g, and a large pore volume of ∼0.68 cm(3) g(-1). When used as anodes for LIBs, the resultant nanosheets show a high reversible capacity (∼145 mAh/g), good rate capability, and long cycling life (capacity remains 110 mAh/g after 100 cycles at a current density of 0.2 A/g). We believe that our method represents a new path way to synthesize novel nanostructured graphene-based hybrids for future applications.

Simple fabrication of TiO2/C nanocomposite with enhanced electrochemical performance for lithium-ion batteries

TiO2/C nanocomposites were fabricated by simple hydrolysis of tetrabutyl titanate to yield TiO2 nanoparticles followed by carbonizing the mixture of glucose and TiO2 at 600°C. By merely varying the weight ratio of glucose:TiO2, the electrochemical performance of the composites could be optimized significantly. At a ratio of 0.8, the composite exhibits a high reversible capacity of 283.7mAhg−1 after cycling 100 times at a current density of 100mAg−1, as well as the capacities of 245.1, 213.6, 179.9 and 136.6mAhg−1 at the corresponding densities of 200, 400, 800 and 1600mAg−1. After cycling 1000 times at 500mAg−1, a capacity of 122.8mAhg−1 was retained for the composite with a ratio of 0.8, and even a capacity of 149.1mAhg−1 for the composite with a ratio of 0.7. The enhanced performance is ascribed to the carbon-coated TiO2 nanoparticles uniformly embedding in the carbon matrix with appropriate carbon content.

Carbon-coated anatase titania as a high rate anode for lithium batteries

Anatase titania nanorods/nanowires, and TiO2(B) are synthesized via a hydrothermal reaction of commercial TiO2 (P-25) in strong alkaline environment. Surfaces of these products are modified by carbon to improve the electrical conductivity through carbonization of pitch as the carbon source at 700 °C for 2 h in an Ar atmosphere. Even after carbon coating, the resultants exhibit the same crystal structure and morphology as confirmed by Rietveld refinement of x-ray diffraction data and transmission electron microscopic observation that the images display thin carbon coating layers on the surfaces of anatase nanorods and nanowires. Although the bare and carbon-coated anatase TiO2 nanorods exhibit stable cycling performance, the high rate performance is highly dependent on the presence of carbon because of high electrical conductivity, ∼10−1 S cm−1, enabling Li+ ion storage even at 30°C (9.9 A g−1) approximately 100 mAh (g-TiO2)−1 for the carbon-coated anatase TiO2 nanorods. Besides, the bare and carbon-coated anatase TiO2 nanowires show poor electrode performances due to their large particle size and high crystallinity causing Li+ insertion into the host structure difficult. It is believed that the conducting carbon coating layers greatly improves the electrochemical property through the improved electrical conductivity and shortened diffusion path.

High cyclability of carbon-coated TiO2 nanoparticles as anode for sodium-ion batteries

Owing to the merits of good chemical stability, elemental abundance and nontoxicity, titanium dioxide (TiO2) has drawn increasing attraction for use as anode material in sodium-ion batteries. Nanostructured TiO2 was able to achieve high energy density. However, nanosized TiO2 is typically electrochemical instable, which leads to poor cycling performance. In order to improve the cycling stability, carbon from thermolysis of poly(vinyl pyrrolidone) was coated onto TiO2 nanoparticles. Electronic conductivity and electrochemical stability were enhanced by coating carbon onto TiO2 nanoparticles. The resultant carbon-coated TiO2 nanoparticles exhibited high reversible capacity (242.3mAhg−1), high coulombic efficiency (97.8%), and good capacity retention (87.0%) at 30mAg−1 over 100 cycles. By comparison, untreated TiO2 nanoparticles showed comparable reversible capacity (237.3mAhg−1) and coulombic efficiency (96.2%), but poor capacity retention (53.2%) under the same condition. The rate performance of carbon-coated TiO2 nanoparticles was also displayed as high as 127.6mAhg−1 at a current density of 800mAg−1. The improved cycling performance and rate capability were mostly attributed to protective carbon layer helping stablize solid electrolyte interface formation of TiO2 nanoparticles and improving the electronic conductivity. Therefore, it is demonstrated that carbon-coated TiO2 nanoparticles are promising anode candidate for sodium-ion batteries.

A high-capacity TiO2/C negative electrode for sodium secondary batteries with an ionic liquid electrolyte

Carbon-coated TiO2 (TiO2/C) nanopowders were synthesized as a negative electrode material for sodium secondary batteries. The TiO2/C negative electrode delivers a high reversible discharge capacity of 275 mA h g−1 at 10 mA g−1 at 363 K.

Preparation and microwave absorption properties of uniform TiO2@C core–shell nanocrystals

Uniform carbon-coated TiO2 core–shell nanocrystals are synthesized and can be used as a new type of broadband microwave absorber.

Carbon-Coated Anatase TiO2 Nanotubes for Li- and Na-Ion Anodes

Carbon-coated, anatase titanium dioxide nanotubes were prepared by carbonizing a polyacrylonitrile-based block copolymer grafted on the as-synthesized titanate nanotubes. As revealed by high resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS), this approach results in a very homogeneous and thin carbon coating, which is advantageous for those active materials storing lithium without undergoing significant volume changes upon ion (de-)insertion. As a matter of fact, thus prepared carbon-coated TiO2 nanotubes presented an excellent long-term cycling stability for more than 500 cycles (0.02% capacity fading per cycle) and a very promising high rate performance (about 130 and 110 mAh g−1 at 10 C and 15 C, respectively). The influence of the tubular morphology on the rate performance is briefly discussed by comparing carbon-coated nanotubes and nanorods. Finally, the carbon-coated nanotubes were also investigated as sodium-ion anode material, showing very promising reversible capacities of around 170, 120, and 100 mAh g−1 at C/10, 1 C, and 2 C, respectively, rendering them as versatile anode material for lithium- and sodium-ion applications

High electrochemical performances of microsphere C-TiO₂ anode for sodium-ion battery.

High-power, long-life carbon-coated TiO2 microsphere electrodes were synthesized by a hydrothermal method for sodium ion batteries, and the electrochemical properties were evaluated as a function of carbon content. The carbon coating, introduced by sucrose addition, had an effect of suppressing the growth of the TiO2 primary crystallites during calcination. The carbon coated TiO2 (sucrose 20 wt % coated) electrode exhibited excellent cycle retention during 50 cycles (100%) and superior rate capability up to a 30 C rate at room temperature. This cell delivered a high discharge capacity of 155 mAh g(composite)(-1) at 0.1 C, 149 mAh g(composite)(-1) at 1 C, and 82.7 mAh g(composite)(-1) at a 10 C rate, respectively.

Preparation and characterisation of carbon‐modified TiO 2 composite

Carbon-modified TiO2 composite was synthesised via the template method and multi-step calcinations by using a tinfoil package. The carbon-coated TiO2 (C–TiO2) composite was characterised via X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and N2 sorption and thermogravimetry. TiO2 was wrapped up in a carbon layer with a thickness of less than 1 nm. The specific surface area and pore volume of C–TiO2 were 95.6 m2g−1 and 0.247 cm3g−1, respectively. The C–TiO2 composite exhibited mesopore structures, showed preferable adsorption capacity for methyl orange and had a higher photocatalytic activity than its unmodified counterpart.

Low-temperature selective catalytic oxidation of ammonia over the CuO x /C-TiO2 catalyst

Carbon-coated TiO2 (C-TiO2) was synthesized by nano-anatase powders and absolute alcohol with chemical vapor deposition method in nitrogen (N2) atmosphere. The CuO x /C-TiO2 composite was prepared as a catalyst for the selective catalytic oxidation (SCO) of ammonia (NH3) and demonstrated both high catalytic activity and low NO yield. Microstructures and properties of these materials were characterized by X-ray diffraction, transmission electron microscopy, and Raman spectra (Raman). The catalytic activity for NH3 oxidation was promoted by introducing carbon into TiO2. NH3 oxidation efficiencies of 44 and 74 % could be obtained at 175 and 200 °C, respectively, under a gas hourly space velocity of 76,000 h−1. The CuO x /C-TiO2 composite was shown with higher catalytic activities than the CuO x /TiO2 catalyst because of the finer CuO x particles and CuO x species by the presence of the carbon layer. The C-TiO2 was a very favorable support for the SCO of NH3 at low temperature.

Amorphous carbon-coated TiO2 nanocrystals for improved lithium-ion battery and photocatalytic performance

10-time lithium rate improvement and 4-time photocatalytic performance enhancement have been achieved with TiO2 nanocrystals when coated with a thin layer of amorphous carbon. The enhanced performances can be attributed to lower lithium ion diffusion and electronic conduction resistance across the carbon layer into the TiO2 electrode material and better surface adsorption of the dye molecules and ions. Thus, the current study may provide us an alternative approach in improving the performances of TiO2 nanocrystals in both lithium ion battery and photocatalysis applications.