We report the growth of linked silicon/carbon (Si/C) nanospheres on Cu substrate as an integrated anode for Li-ion batteries. The Si/C nanospheres were synthesized by a catalytic chemical vapor deposition (CCVD) on Cu substrate as current collector using methyltrichlorosilane as precursor, a cheap by-product of the organosilane industry. The samples were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, thermal gravimetry, Raman spectroscopy, nitrogen adsorption, inductively coupled plasma optical emission spectrometry, and X-ray photoelectron spectroscopy. It was found that the linked Si/C nanospheres with a diameter of 400–500 nm contain Si, CuxSi, and Cu nanocrystals, which are highly dispersed in the amorphous carbon nanospheres. A CCVD mechanism was tentatively proposed, in which the evaporated Cu atoms play a critical role to catalytically grown Si nanocrystals embedded within linked Si/C nanospheres. The electrochemical measurement shows that these Si/C nanospheres delivered a capacity of 998.9, 713.1, 320.6, and 817.8 mA h g−1 at 50, 200, 800, and 50 mA g−1 respectively after 50 cycles, much higher than that of commercial graphite anode. This is because the amorphous carbon, CuxSi, and Cu in the Si/C nanospheres could buffer the volume change of Si nanocrystals during the Li insertion and extraction reactions, thus hindering the cracking or crumbling of the electrode. Furthermore, the incorporation of conductive CuxSi and Cu nanocrystals and the integration of active electrode materials with Cu substrate may improve the electrical conductivity from the current collector to individual Si active particles, resulting in a remarkably enhanced reversible capacity and cycling stability. The work will be helpful in the fabrication of low cost binder-free Si/C anode materials for Li-ion batteries.

A general synthetic method based on a solvothermal route for the preparation of multiple transition metal oxide (MTMO) mesoporous nanospheres (ZnaNibMncCodFe2O4, 0 ≤ a, b, c, d ≤ 1, a + b + c + d = 1) with controllable composition and uniform size distribution has been developed. The as-prepared ZnaNibMncCodFe2O4 nanospheres are formed by self-assembly of nanocrystals with the size of 5–10 nm via structure-directing agents and mineralizer coordinating effect as well as optimization of the synthesis conditions. It has been identified that the addition of mineralizer is crucial for the control of the nucleation process when the metallic precursors are reduced; meanwhile the structure-directing agent is key to forming the mesoporous structure. A number of characterization techniques including X-ray diffraction, transmission electron microscopy, scanning electron microscopy, inductively coupled plasma optical emission spectrometry, temperature-programmed reduction, and nitrogen adsorption have been used to characterize the as-prepared mesoporous products. The overall strategy in this work extends the controllable fabrication of high-quality MTMO mesoporous nanospheres with designed components and compositions, rendering these nanospheres with promising potential for various applications (oxygen reduction reaction, magnetic performance, supercapacitor, lithium-ion batteries, and catalysis).

•Li[Li0.2Mn0.56Ni0.16Co0.08]O2 was synthesized by solid-state method.•Effects of calcination temperature, time, and quenching methods were investigated.•Material synthesized at 800 °C for 12 h and quenched in air shows best electrochemical property.Layered Li[Li0.2Mn0.56Ni0.16Co0.08]O2 cathode materials were synthesized via a solid-state reaction for Li-ion batteries, in which lithium hydroxide monohydrate, manganese dioxide, nickel monoxide, and cobalt monoxide were employed as metal precursors. To uncover the relationship between the structure and electrochemical properties of the materials, synthesis conditions such as calcination temperature and time as well as quenching methods were investigated. For the synthesized Li[Li0.2Mn0.56Ni0.16Co0.08]O2 materials, the metal components were found to be in the form of Mn4+, Ni2+, and Co3+, and their molar ratio was in good agreement with stoichiometric ratio of 0.56:0.16:0.08. Among them, the one synthesized at 800 °C for 12 h and subsequently quenched in air showed the best electrochemical performances, which had an initial discharge specific capacity and coulombic efficiency of 265.6 mAh/g and 84.0%, respectively, and when cycled at 0.5, 1, and 2 C, the corresponding discharge specific capacities were 237.3, 212.6, and 178.6 mAh/g, respectively. After recovered to 0.1 C rate, the discharge specific capacity became 259.5 mAh/g and the capacity loss was only 2.3% of the initial value at 0.1 C. This work suggests that the solid-state synthesis route is easy for preparing high performance Li[Li0.2Mn0.56Ni0.16Co0.08]O2 cathode materials for Li-ion batteries.

We report the preparation and characterization of amorphous silicon–carbon (Si–C) nanospheres as anode materials in Li-ion batteries. These nanospheres were synthesized by a chemical vapor deposition at 900 °C using methyltrichlorosilane (CH3SiCl3) as both the Si and C precursor, which is a cheap byproduct in the organosilane industry. The samples were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, nitrogen adsorption, thermal gravimetric analysis, Raman spectroscopy, and X-ray photoelectron spectroscopy. It was found that the synthesized Si–C nanospheres composed of amorphous C (about 60 wt%) and Si (about 40 wt%) had a diameter of 400–600 nm and a surface area of 43.8 m2 g−1. Their charge capacities were 483.6, 331.7, 298.6, 180.6, and 344.2 mA h g−1 at 50, 200, 500, 1000, and 50 mA g−1 after 50 cycles, higher than that of the commercial graphite anode. The Si–C amorphous structure could absorb a large volume change of Si during Li insertion and extraction reactions and hinder the cracking or crumbling of the electrode, thus resulting in the improved reversible capacity and cycling stability. The work opens a new way to fabricate low cost Si–C anode materials for Li-ion batteries.

We report the synthesis and characterization of mesoporous cobalt ferrite (CoFe2O4, named CFO) nanospheres cross-linked by carbon nanotubes (CNTs) as anode nanocomposites (CFO/CNT) for Li-ion batteries. CFO/CNT nanocomposites were synthesized by a facile one-pot solvothermal method using Co(CH3COO)2 and FeCl3 as the metal precursors in the presence of CH3COOK, CH3COOC2H5, HOCH2CH2OH, and CNTs. The obtained samples were characterized by X-ray diffraction, thermogravimetric analysis, nitrogen adsorption, transmission electron microscopy, and scanning electron microscopy. It is found that most CFO nanospheres are interconnected with CNTs forming a network composite possibly due to the presence of defects at the open ends and on the external surface of CNTs. These defects may act as nucleation centers for growth of CFO nanospheres. Compared with the bare CFO nanospheres and the physically mixed CFO nanospheres with CNTs, the CFO/CNT composite containing 16.5 wt% CNTs shows much higher capacities of 1137.6, 1003.4, 867.3, and 621.7 mA h g−1 at the current densities of 200, 500, 1000, and 2000 mA g−1 after 10 charge–discharge cycles, respectively, and even after 100 cycles, it still maintains a high capacity of 1045.6 mA h g−1 at 200 mA g−1. The super electrochemical properties of the CFO/CNT composite should originate from the formed network structure with the intimate interconnection between CFO nanospheres and CNTs, which not only provides stable electrical and ionic transfer channels but also significantly shortens the diffusion length of the Li+ ions. This work opens a new way for fabrication and utilization of metal oxide–CNT composites as anode materials for Li-ion batteries.

We report a facile chemical vapor deposition (CVD) method to grow silicon/carbon (Si/C) microrods on the surface of commercial graphite microspheres (GMs) to prepare Si/C/GM composite materials as Li-ion battery anodes. Dimethyldichlorosilane and toluene were used as Si and C precursors, respectively. The CVD temperature and time, as well as the mechanism of materials growth were investigated. The samples were characterized by using X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. It was found that the obtained Si/C/GM composites with an urchin-like morphology are composed of Si particles, amorphous carbon, and graphite. The CVD conditions have a significant impact on the morphology and electrochemical performance of the composite materials. The composite prepared under the optimum CVD conditions, namely at 900 °C for 5 h, displayed the best anode properties with a specific capacity of 562.0 mA h g−1 at a current density of 50 mA g−1, much higher than that of GMs (361.0 mA h g−1), and a good cycling performance (i.e., a reversible capacity of 590.5 mA h g−1 after 50 cycles). The improved electrochemical performance is attributed to the incorporation of Si, together with the formation of a Si/C microrod network, which connects the GMs and buffers the volume change of Si during lithium ion insertion/extraction. The work provides a simple and low-cost route to enhance the performance of commercial graphite anode materials for Li-ion batteries.

We report the decoration of commercial graphite microspheres (GMs) with Si particles as anode materials for Li-ion batteries. The Si particles are obtained from solid Si waste of organosilane industry that is acid-washed to remove the impurities and further ground. The GMs with a size of 5–40 μm as main active material, Si particles with a size of 1–10 μm as an additive, and sucrose dissolved in water as a binder are mixed and followed by carbonization to obtain Si/C composites containing graphite, Si, and amorphous carbon generated from sucrose. It is found that the composite containing 60.5 wt% of GMs, 22.1 wt% of Si, and 17.4 wt% of amorphous carbon obtained at 800 °C for 5 h shows the best electrochemical performance with a specific capacity of 522.6 mA h g−1 at the current density of 50 mA g−1 and 306.9 mA h g−1 at 500 mA g−1, much higher than those of GMs. Its capacity retention at 500 mA g−1 attains 93.9% after 20 cycles. The work demonstrates the possibility for utilization of the industrial Si waste to enhance graphite anode materials in Li-ion batteries.Highlights► Si waste from organosilane industry was used for preparation of Si/C composite. ► Graphite microspheres were decorated with Si particles and sucrose as the binder. ► The Si/C composite anodes show the enhanced electrochemical performance.

A series of α-Al2O3-supported Ni catalysts with different Ni particle sizes (5–10, 10–20, and 20–35 nm) were prepared and applied in the CO methanation reaction for the production of synthetic natural gas (SNG). The catalytic tests showed that the Ni nanoparticles influenced the catalytic performance in the CO methanation, and the catalyst with a Ni nanoparticle size of 10–20 nm showed the highest CO conversion, CH4 yield, and turnover frequency, and the lowest carbon deposition, demonstrating the possibility of improving the Ni/α-Al2O3 catalysts in the CO methanation for SNG production by controlling their Ni particle size.

Nickel catalysts supported on the perovskite oxide CaTiO3 (CTO) were prepared by an impregnation method for CO methanation to produce synthetic natural gas (SNG). X-Ray diffraction, nitrogen adsorption, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, H2-temperature programmed reduction and desorption, and X-Ray photoelectron spectroscopy were employed for the characterization of samples. The results revealed that the Ni/CTO catalysts showed a better performance than Ni/Al2O3 for CO methanation at various reaction conditions. The life time test at 600 °C and 3.0 MPa indicates that Ni/CTO is also more active, thermally stable and resistant to carbon deposition. This is because of the relatively weak Ni–CTO support interaction, highly stable CTO support, the absence of acidic sites on the surface of CTO and the proper Ni particle size of about 20–30 nm. The work is important for the development of effective methanation catalysts for SNG production.

•CuCl microcrystals with different morphologies were solvothermally synthesized.•Cu(C5H7O2)2 was identified to be the key intermediate in the conversion process.•These CuCl microcrystals show higher activity for dimethyldichlorosilane synthesis.CuCl microcrystals with different morphologies such as tetrahedra, etched tetrahedra, tripod dendrites, and tetrapods were synthesized using CuCl2⋅2H2O as the copper precursor in the mixed solvent of acetylacetone and ethylene glycol. The samples were characterized with X-ray diffraction, scanning electron microscopy, infrared spectroscopy, and transmission electron microscope. Cu(C5H7O2)2 was identified as the key intermediate, and the morphology and structure of the CuCl microcrystals were highly dependent on the reaction time and temperature, as well as the volume of the solvents. The catalytic properties of these CuCl microcrystals were explored in the dimethyldichlorosilane synthesis via Rochow reaction. Compared to the commercial CuCl microparticles with irregular morphology and dense internal structure, the obtained CuCl microcrystals possessed regular morphology and different exposed crystal planes and showed much higher dimethyldichlorosilane selectivity and Si conversion via the Rochow reaction because of the enhanced formation of active CuxSi phase and gas transportation within the dendritic structure, demonstrating the significance of regular morphology of the copper-based catalysts in catalytic organosilane synthesis.

We report the synthesis and characterization of the mesoporous manganese ferrite (MnFe2O4) microspheres as anode materials for Li-ion batteries. MnFe2O4 microspheres were synthesized by a facile solvothermal method using Mn(CH3COO)2 and FeCl3 as metal precursors in the presence of CH3COOK, CH3COOC2H5, and HOCH2CH2OH. The samples were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, nitrogen adsorption, thermal gravimetric, X-ray photoelectron spectroscopy, temperature programmed reduction, and temperature programmed oxidation. The synthesized mesoporous MnFe2O4 microspheres composed of nanoparticles (10–30 nm) were 100–500 nm in diameter and had surface areas between 60.2 and 86.8 m2 g−1, depending on the CH3COOK amounts added in the preparation. After calcined at 600 °C, MnFe2O4 was decomposed to Mn2O3 and Fe2O3 mixture. The mesoporous MnFe2O4 microspheres calcined at 400 °C showed a capacity of 712.2 mA h g−1 at 0.2 C and 552.2 mA h g−1 at 0.8 C after 50 cycles, and an average capacity fading rate of around 0.28%/cycle and 0.48%/cycle, much better than those of the samples without calcination and calcined at 600 °C. The work would be helpful in the fabrication of binary metal oxide anode materials for Li-ion batteries.Graphical abstractHighlights► Mesoporous MnFe2O4 microspheres were synthesized using solvothermal method. ► Obtained mesoporous MnFe2O4 microspheres had high surface areas (60.2–86.8 m2 g−1). ► After calcined at 600 °C, MnFe2O4 microspheres were decomposed to Mn2O3 and Fe2O3. ► The mesoporous MnFe2O4 calcined at 400 °C showed the best electrochemical property.

We report the simple preparation of the barium hexaaluminate (BaO·6Al2O3, BHA) with high surface area (BHA-HSA) (>100 m2 g−1) through a coprecipitation method using carbon black as the hard template. Ni catalysts supported on BHA-HSA (Ni/BHA-HSA) with different NiO loadings (10, 20, and 40 wt%) were investigated in CO methanation for the production of synthetic natural gas (SNG). The CO methanation reaction was carried out at 0.1 and 3.0 MPa with a weight hourly space velocity of 30000 mL g−1 h−1. It was found that Ni/BHA-HSA catalysts showed increased activity at low temperature (240–400 °C) compared with more conventional Ni/BHA catalysts with the same NiO loadings. A highest CH4 yield of 95.7% can be obtained over Ni/BHA-HSA (40 wt% of NiO loading) at 400 °C and 3.0 MPa, and a lifetime test shows that, at 500 °C and 3.0 MPa, it is more stable than Ni/BHA. The serious aggregation of Ni nanoparticles is the major reason for the deactivation of the latter. The work demonstrates that BHA-HSA can be effectively prepared using carbon black as the hard template and is more suitable as a Ni catalyst support for CO methanation.

We report the application of partially reduced CuO nanoparticles as Cu-based catalysts for dimethyldichlorosilane (M2) synthesis via the Rochow reaction. The CuO nanoparticles (50–100 nm) were synthesized by a simple precipitation method and partially reduced in a H2/N2 mixture gas to obtain the Cu-based catalyst containing different Cu species of CuO, Cu2O, and Cu. It was found that the composition of the samples could be tailored by varying the volume ratio of H2/N2 at the given reduction temperature and time. Compared to the synthesized CuO and Cu nanoparticles, as well as the commercial CuO microparticles, these multicomponent Cu-based catalysts, particularly for the CuO–Cu2O–Cu catalyst, showed much higher M2 selectivity and Si conversion in the Rochow reaction. The enhanced catalytic performance is attributed to the smaller particle size and the synergistic effect among the different components. The work would help to develop novel ternary Cu-based catalysts for organosilane synthesis.

We report in situ growth of mesoporous Mn0.5Co0.5Fe2O4 (MCFO) nanospheres on graphene to form MCFO/graphene nanocomposites by a facile solvothermal method. In the synthesis, Mn(CH3COO)2, Co(CH3COO)2, and FeCl3 were used as the metal precursors and CH3COOK, CH3COOC2H5, and HOCH2CH2OH as the mixed solvent. The obtained MCFO nanospheres (50–200 nm) were composed of small nanoparticles (5–15 nm), and the graphene surface acted as the nucleation sites in growing MCFO nanospheres. Compared with the bare MCFO nanospheres and the MCFO nanospheres physically mixed with graphene, the MCFO/graphene nanocomposite with 2.1 wt % graphene as anode material in Li ion batteries showed a significantly enhanced electrochemical performance with high lithium storage capacity and excellent cycling stability. This is because the introduced graphene can prevent the aggregation of nanospheres and provides a pathway for excellent Li+ ion diffusion and electronic conduction. This work opens a way for facile fabrication of metal oxide/graphene nanocomposites.

We report the preparation of high surface area hedgehog-like CuO microspheres by a wet-chemical method and their application in Li-ion batteries used as anode materials. The samples were characterized by Nitrogen adsorption, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, temperature-programmed reduction and thermogravimetric analysis. The synthesized hedgehog-like CuO microspheres with a size of 1–3 um possessed a high surface area of 103.5–157.4 m2 g−1 and an average crystal size of 7–9 nm. When used as anode materials, they showed an initial discharge and charge capacity of 1294.6 and 647.6 mAh g−1, respectively, much higher than the corresponding values of the low surface area CuO microspheres, which are 967.1 and 382.6 mAh g−1 respectively. After calcination at 300 and 600 °C, the morphology of hedgehog-like CuO microspheres was still maintained, and a high capacity of 570–590 mAh g−1 at 0.1 C was observed after 50 cycles. Meanwhile, the average capacity fading rates for calcined hedgehog-like CuO microspheres were much lower than that of non-calcined and low surface area CuO microspheres, demonstrating that the calcination of CuO microspheres with the high surface area leads to a better cycling performance. This work provides a new method to prepare high surface area CuO materials, which are promising anode materials with high capacity and long cycling life in Li-ion batteries.Graphical abstractHighlights► The hedgehog-like CuO microspheres with a high surface area were synthesized. ► The CuO microspheres as anode materials showed a higher capacity than solid CuO. ► Calcination at high temperature could enhance electrochemical properties of CuO.

Phase-pure Cu4O3 microspheres were synthesized for the first time via a facile solvothermal method, using Cu(NO3)2·3H2O as the precursor. A formation mechanism was proposed based on the observation of a series of reaction intermediates. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, temperature-programmed reduction and oxidation, X-ray photoelectron spectroscopy, and nitrogen adsorption. It was found that the composition of the prepared products were highly dependent on the synthesis conditions, particularly the hydrate water content in the copper precursor of Cu(NO3)2. Pure Cu4O3 microspheres with a diameter of 2–10 μm could be obtained via the symproportionation reaction (2CuO + Cu2O → Cu4O3), which was regarded not being feasible in aqueous media under mild synthesis conditions. The electrochemical properties of the Cu4O3 microspheres as anode materials for Li-ion batteries were also investigated. Compared to the simple physical mixture of CuO and Cu2O with an equivalent atomic ratio of 2:1, the as-prepared Cu4O3 exhibited unique lithium storage behaviors at a low voltage range and superior electrochemical performances as an anode material for Li-ion batteries. The successful preparation of pure Cu4O3 material could provide opportunities to further explore its physicochemical properties and potential applications.Keywords: anode materials; characterization; Li-ion batteries; phase-pure Cu4O3 microspheres; solvothermal synthesis;

Polymer/graphene composites have attracted much attention due to their unique organic–inorganic hybrid structure and exceptional properties. In this paper, we report the synthesis of polystyrene/reduced graphene oxide (PS/r-GO) composites by a two-step in situ reduction technique, which consists of a hydrazine hydrate reduction and a subsequent thermal reduction at 200 °C for 12 h. The structure and micromorphology of PS/r-GO composites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis. The results show that the GO can be efficiently reduced by the two-step in situ reduction method, and the r-GO sheets are well dispersed and ultimately form a continuous network structure in the polymer matrix. PS/r-GO composite films (5 wt% GO) are prepared by the hot press molding method, possessing a conductivity as high as 22.68 S m−1. The superior conductivity arises from the high reduction degree of GO and its high dispersion and the formation of a network structure in the polymer matrix. These polymer/r-GO composites are expected to be applied in multiple electric devices. The techniques for preparing polymer/r-GO composite films could be further extended to other similar systems.

We report the preparation and characterization of metal–carbon nanocomposites (NiRuC, FeRuC, and CoRuC) with bimetallic Ni–Ru, Fe–Ru, and Co–Ru nanoparticles incorporated into the pore walls of ordered mesoporous carbon, which were synthesized via a template strategy. Pt nanoparticles were deposited on the nanocomposites separately, which is different from the traditional alloying method. Nitrogen adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and thermogravimetric analysis techniques were used to characterize the materials. It was found that bimetallic nanoparticles (Ni–Ru, Fe–Ru, and Ru–Co) are homogenously dispersed in the carbon matrix and Pt nanoparticles with a size of less than 5 nm are widely distributed within the nanocomposites. The Pt/CoRuC catalyst shows better catalytic activity for the methanol oxidation reaction (MOR) than Pt on FeRuC or NiRuC, and its performance is also closer to that of the commercial PtRu catalyst with a slightly higher metal loading. A kinetic-based impedance model was used to simulate the electrochemical properties of the catalysts and matches well with the MOR performances of the catalysts. The promotional effect of the bimetallic/carbon nanocomposites on the catalytic activity of Pt was evidenced, and more importantly, the ligand effect was demonstrated by our results to be the major factor in the enhancement. Our investigation not only provides further insight into the roles of Fe, Ni and Co in MOR, but also assists in the design and synthesis of the new types of nanostructured electrocatalyst supports.

Porous cubic Cu microparticles were synthesized by a facile solvothermal method using Cu(CH3COO)2·H2O as the Cu precursor and NaOH in a solution containing ethanol, ethylene glycol, and water. The synthesis conditions were investigated and a growth process of porous cubic Cu microparticles was proposed. The catalytic properties of the porous Cu microparticles as model copper catalysts for Rochow reaction were explored. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, temperature-programmed reduction, and nitrogen adsorption. It was found that the morphology and structure of the porous cubic Cu microparticles are highly dependent on the reaction time and temperature as well as on the amount of reactants added. Compared to the commercial Cu microparticles with irregular morphology and dense internal structure, porous cubic Cu microparticles show much higher dimethyldichlorosilane selectivity and Si conversion via Rochow reaction, which are attributed to the enhanced formation of active CuxSi phase and gas transportation in the presence of the pore system within microparticles, demonstrating the significance of the pore structure of the copper catalysts in catalytic reactions of organosilane synthesis.Keywords: copper catalysts; porous cubic Cu microparticles; Rochow reaction; solvothermal method;

We report the comparative investigation on the electrochemical application of mesoporous copper oxide (Cu2O and CuO) microspheres with different surface areas as anode materials in Li-ion batteries. Mesoporous Cu2O microspheres with a narrow particle size distribution are synthesized by a hydrothermal method and CuO is obtained by subsequent oxidation of Cu2O. The synthesized mesoporous Cu2O and CuO microspheres possess a surface area of 12.7–65.8 and 5.2–37.6 m2 g−1 and an average crystal size of 15.0–20.5 and 10.4–15.9 nm, respectively. The result reveals that the mesoporous Cu2O and CuO microspheres with a higher surface area show a higher capacity and better cyclability than those with a lower surface area. The mesoporous Cu2O and CuO microspheres with a surface area of 65.8 and 37.6 m2 g−1 show an initial charge capacity of 430.5 mAh g−1 and 601.6 mAh g−1 and deliver a capacity as high as 355.2 mAh g−1 and 569.8 mAh g−1 at 0.1 C after 50 cycles, respectively. This is because the highly developed mesoporous structure can enhance the accommodation of lithium ions, shorten the diffusion distance for lithium ions, and increase the absorption of electrolyte.Highlights► Mesoporous copper oxide microspheres with different surface areas were prepared. ► Mesoporous copper oxides with high surface area show improved anode properties. ► Developed pore structure causes more accommodation and fast diffusion for Li ions.

We report the preparation and characterization of mesoporous carbon nanocomposites with Ni and Co nanoparticles incorporated into the pore walls, which are synthesized via template strategy by sucrose-impregnation and benzene chemical vapor deposition (CVD) routes separately. Pt nanoparticles supported on the nanocomposites for oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) in fuel cells are fabricated via hydrogen reduction method. It is found that the introduction of metal nanoparticles into the pore walls of carbon materials via both synthesis routes had negligible change in pore structure. Highly dispersed Pt nanoparticles supported on nanocomposites synthesized by sucrose-impregnation method shows better catalytic activities for both ORR and MOR than that on those by CVD method and greatly improve the limiting current densities for ORR. The promotional effect of Ni on the catalytic activity of Pt catalysts for both ORR and MOR is evidenced in nanocomposites obtained with sucrose-impregnation method, but not with CVD method. Interesting results revealed that Ni performed as a better promoter in MOR while Co is a better promoter in ORR. Our investigation not only provides further insight on the roles of Ni and Co in ORR and MOR, but also can assist the design and synthesis of the new nanostructured electrocatalyst supports.Highlights► Ordered mesoporous carbon nanocomposites with Ni and Co nanoparticles incorporated in the pore walls of carbon were prepared with template methods. ► Highly dispersed Pt nanoparticles supported on nanocomposites were synthesized via hydrogen reduction method. ► Ni and Co nanoparticles within carbon supports have significant effect on methanol oxidation reaction and oxygen reduction reaction of fuel cells.

Hierarchical dandelion-like CuO (HD–CuO) microspheres composed of nanoribbons were prepared via a facile hydrothermal method. The samples were characterized by nitrogen adsorption, X-ray diffraction, temperature-programmed reduction, thermogravimetric analysis, transmission electron microscopy and scanning electron microscopy. It was found that the reaction temperature, reaction time and reagent amounts had a significant effect on the morphology and structure of HD–CuO. The obtained HD–CuO microspheres possessed a surface area of 10.6–57.5 m2 g−1 and a diameter of 3–6 μm. In the formation process, ethylene glycol was adsorbed on the surface of the CuO nanoribbons and it acted as the structure-directing agent and thereafter the CuO nanoribbons were self-assembled into HD–CuO. The investigation of the Rochow reaction showed that the HD–CuO catalyst had a better catalytic performance in dimethyldichlorosilane synthesis than the commercial CuO microparticles and commercial CuO–Cu2O–Cu catalyst, owing to its well-developed hierarchically porous structure and higher specific surface area, leading to the increased contact interface among reaction gas, solid catalyst and solid silicon, together with enhanced mass transportation.

We report the preparation of Cu2O microparticles with different shapes, by simple hydrolyzation and reduction of copper acetate with glucose in a mixture of water–ethanol solvent. The effect of the synthesis conditions on the shape of the Cu2O microparticles and their catalytic properties in the Rochow reaction were investigated. The samples were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, temperature-programmed reduction, and thermogravimetric analysis. Cu2O microparticles with different shapes, such as hexahedron, ananas-like, sphere-like, and star-like shapes, with particle sizes of 2–4 μm, were obtained by tuning the volume ratio of water:ethanol. The hexahedron Cu2O microparticles were found to exhibit the best catalytic performance for the synthesis of dimethyldichlorosilane via the Rochow reaction. This work should be helpful in the design and development of novel copper catalysts for organosilane synthesis and understanding their catalytic roles.

Urchin-like ZnO microspheres were successfully prepared by thermal decomposition of hydrozincite synthesized via homogeneous precipitation of zinc nitrate and urea in the presence of a nonionic surfactant polyethylene glycol. The synthesis conditions, such as reaction temperature and time, precursor concentration, and the amount of surfactant added, as well as the catalytic properties of urchin-like ZnO microspheres as promoters for a commercial copper catalyst in dimethyldichlorosilane synthesis were investigated. In addition, the formation mechanism of urchin-like microspheres from hydrozincite to ZnO was proposed. The ZnO samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and N2 adsorption. It was found that zinc nitrate concentration and the amount of surfactant are the key factors that lead to the formation of urchin-like ZnO microspheres. These ZnO samples had BET surface areas of 16–30 m2 g−1 and an average diameter of 3–8 μm. Compared with commercial Zn microspheres and ZnO nanoparticles, urchin-like ZnO microspheres showed a better performance in dimethyldichlorosilane synthesis via the Rochow reaction due to their larger surface area, which created more interfacial contacts with the copper catalyst and active Cu3Si species. The work is helpful for developing novel catalyst promoters and understanding the role of the promoter in the Rochow reaction.

Synthetic natural gas (SNG) can be obtained via methanation of synthesis gas (syngas). Many thermodynamic reaction details involved in this process are not yet fully understood. In this paper, a comprehensive thermodynamic analysis of reactions occurring in the methanation of carbon oxides (CO and CO2) is conducted using the Gibbs free energy minimization method. The equilibrium constants of eight reactions involved in the methanation reactions were calculated at different temperatures. The effects of temperature, pressure, ratio of H2/CO (and H2/CO2), and the addition of other compounds (H2O, O2, CH4, and C2H4) in the feed gas (syngas) on the conversion of CO and CO2, CH4 selectivity and yield, as well as carbon deposition, were carefully investigated. In addition, experimental data obtained on commercial Ni-based catalysts for CO methanation and three cases adopted from the literature were compared with the thermodynamic calculations. It is found that low temperature, high pressure, and a large H2/CO (and H2/CO2) ratio are favourable for the methanation reactions. Adding steam into the feed gas could alleviate the carbon deposition to a large extent. Trace amounts of O2 in syngas is unfavourable for SNG generation although it can lower carbon deposition. Additional CH4 in the feed gas almost has no influence on the CO conversion and CH4 yield, but it leads to the increase of carbon formed. Introduction of a small amount of C2H4, a representative of hydrocarbons in syngas, results in low CH4 yield and serious carbon deposition although it does not affect CO conversion. CO is relatively easy to hydrogenated compared to CO2 at the same reaction conditions. The comparison of thermodynamic calculations with experimental results demonstrated that the Gibbs free energy minimization method is significantly effective for understanding the reactions occurring in methanation and helpful for the development of catalysts and processes for the production of SNG.

Flower-like CuO microspheres synthesized by a facile hydrothermal method were found to be an effective catalyst for the Rochow reaction with a higher dimethyldichlorosilane selectivity and Si conversion because of the enhanced formation of an active CuxSi phase and mass transport.

Mesoporous Cu2O (MP-Cu2O) microspheres were prepared via a facile template-free hydrothermal synthesis in the open system, in which copper acetate was used as the copper precursor and glucose as a reducing agent. The synthesis conditions and catalytic property of MP-Cu2O for dimethyldichlorosilane synthesis via the Rochow reaction were investigated, and the formation mechanism of MP-Cu2O microspheres was proposed. The samples were characterized by nitrogen adsorption, X-ray diffraction, temperature-programmed reduction, thermogravimetric analysis, transmission electron microscopy, and scanning electron microscopy. It was found that the synthesis conditions such as reaction temperature, time, and reactant amount added have a significant effect on the morphology and pore structure of MP-Cu2O microspheres, and MP-Cu2O microspheres were formed through assembly of Cu2O nanoparticles. MP-Cu2O microspheres with a surface area of 65.8 m2/g, pore size of 26.7 nm, and a diameter of 400–700 nm were obtained under the optimized condition. As compared to the nonporous Cu2O microspheres, MP-Cu2O microspheres showed a better catalytic performance in dimethyldichlorosilane synthesis due to their developed pore structure and high surface area, which allow larger contact interface among the reaction gas, solid catalyst, and the solid reactant, together with enhanced mass transport. The work would be helpful for developing novel structured copper catalysts for organosilane synthesis and for understanding the catalytic mechanism.

CO methanation reaction over the Ni/Al2O3 catalysts for synthetic natural gas production was systematically investigated by tuning a number of parameters, including using different commercial Al2O3 supports and varying NiO and MgO loading, calcination temperature, space velocity, H2/CO ratio, reaction pressure, and time, respectively. The catalytic performance was greatly influenced by the above-mentioned parameters. Briefly, a large surface area of the Al2O3 support, a moderate interaction between Ni and the support Al2O3, a proper Ni content (20 wt %), and a relatively low calcination temperature (400 °C) promoted the formation of small NiO particles and reducible β-type NiO species, which led to high catalytic activities and strong resistance to the carbon deposition, while addition of a small amount of MgO (2 wt %) could improve the catalyst stability by reducing the carbon deposition; other optimized conditions that enhanced the catalytic performance included high reaction pressure (3.0 MPa), high H2/CO ratio (≥3:1), low space velocity, and addition of quartz sand as the diluting agent in catalyst bed. The best catalyst combination was 20–40 wt % of NiO supported on a commercial Al2O3 (S4) with addition of 2–4 wt % of MgO, calcined at 400–500 °C and run at a reaction pressure of 3.0 MPa. On this catalyst, 100% of CO conversion could be achieved within a wide range of reaction temperature (300–550 °C), and the CH4 selectivity increased with increasing temperature and reached 96.5% at a relatively low temperature of 350 °C. These results will be very helpful to develop highly efficient Ni-based catalysts for the methanation reaction, to optimize the reaction process, and to better understand the above reaction.

We report the preparation and characterization of Ni nanoparticles supported on barium hexaaluminate (BHA) as CO methanation catalysts for the production of synthetic natural gas (SNG). BHA with a high thermal stability was synthesized by a coprecipitation method using aluminum nitrate, barium nitrate, and ammonium carbonate as the precursors. The Ni catalysts supported on the BHA support (Ni/BHA) were prepared by an impregnation method. X-ray diffraction, nitrogen adsorption, transmission electron microscopy, thermogravimetric analysis, H2 temperature-programmed reduction, O2 temperature-programmed oxidation, NH3 temperature-programmed desorption, and X-ray photoelectron spectroscopy are used to characterize the samples. The CO methanation reaction was carried out at pressures of 0.1 and 3.0 MPa, weight hourly space velocities (WHSVs) of 30 000, 120 000, and 240 000 mL·g–1·h–1, with a H2/CO feed ratio of 3, and in the temperature range 300–600 °C. The results show that although the BHA support has a relatively low surface area, Ni/BHA catalysts displayed much higher activity than Al2O3-supported Ni catalysts (Ni/Al2O3) with a similar level of NiO loading even after high temperature hydrothermal treatment. Nearly 100% CO conversion and 90% CH4 yield were achieved over Ni/BHA (NiO, 10 wt %) at 400 °C, 3.0 MPa, and a WHSV of 30 000 mL·g–1·h–1. Long time testing indicates that, compared to Ni/Al2O3 catalyst, Ni/BHA is more stable and is highly resistant to carbon deposition. The superior catalytic performance of the Ni/BHA catalyst is probably related to the relatively larger Ni particle size (20–40 nm), the high thermal stability of BHA support with nonacidic nature, and moderate Ni–BHA interaction. The work demonstrates BHA would be a promising alternative support for the efficient Ni catalysts to SNG production.

Porous structure of the electrocatalyst support is of importance for mass transfer of reactants and products in electrochemical reactions of fuel cells. This study reports the comparative investigation of the electrochemical performance of Pt nanoparticles supported on the meso- and microporous carbons as well as commercial Pt catalyst E-TEK (40 wt % Pt loading) for the methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) in fuel cells. Ordered mesoporous carbon (OMC) synthesized using the template method was employed as the representative of mesoporous carbon, and carbon black BP2000 was used as the microporous carbon because of its microporous structure with a high surface area comparable to that of OMC. The samples were characterized by nitrogen adsorption, X-ray diffraction, small-angle X-ray scattering, thermogravimetric analysis, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results showed that, for MOR, the Pt/OMC catalyst possessed a significantly higher catalytic activity measured by cyclic voltammetry than that of Pt/BP2000 and its performance even exceeded that of commercial catalyst E-TEK. The electrochemical impedance measurement indicated that Pt/OMC has a smaller charge-transfer resistance and faster overall MOR rate than both Pt/BP2000 and E-TEK catalysts. In contrast, for ORR, the mass activity of Pt/BP2000 is higher than that of Pt/OMC on a rotating disk electrode but comparable to that of E-TEK. The study may suggest that the mesoporous structure of the carbon support is important for liquid-phase electrochemical reactions, while micropores are more suitable for gas reactions at the electrodes of fuel cells. This work would be helpful in understanding the molecular transport of reactants and products in the pore nanostructure of carbon-supported Pt electrocatalysts for fuel cell application.

The correlation between phase structures and surface acidity of Al2O3 supports calcined at different temperatures and the catalytic performance of Ni/Al2O3 catalysts in the production of synthetic natural gas (SNG) via CO methanation was systematically investigated. A series of 10 wt% NiO/Al2O3 catalysts were prepared by the conventional impregnation method, and the phase structures and surface acidity of Al2O3 supports were adjusted by calcining the commercial γ-Al2O3 at different temperatures (600–1200 °C). CO methanation reaction was carried out in the temperature range of 300–600 °C at different weight hourly space velocities (WHSV = 30000 and 120000 mL·g−1·h−1) and pressures (0.1 and 3.0 MPa). It was found that high calcination temperature not only led to the growth in Ni particle size, but also weakened the interaction between Ni nanoparticles and Al2O3 supports due to the rapid decrease of the specific surface area and acidity of Al2O3 supports. Interestingly, Ni catalysts supported on Al2O3 calcined at 1200 °C (Ni/Al2O3-1200) exhibited the best catalytic activity for CO methanation under different reaction conditions. Lifetime reaction tests also indicated that Ni/Al2O3-1200 was the most active and stable catalyst compared with the other three catalysts, whose supports were calcined at lower temperatures (600, 800 and 1000 °C). These findings would therefore be helpful to develop Ni/Al2O3 methanation catalyst for SNG production.The correlation between the phase structures and surface acidity of the Al2O3 supports calcined at different temperatures and the catalytic performance of Ni/Al2O3 catalysts in CO methanation is systematically investigated.Download full-size image

We report the preparation and characterization of metal–carbon nanocomposites (NiRuC, FeRuC, and CoRuC) with bimetallic Ni–Ru, Fe–Ru, and Co–Ru nanoparticles incorporated into the pore walls of ordered mesoporous carbon, which were synthesized via a template strategy. Pt nanoparticles were deposited on the nanocomposites separately, which is different from the traditional alloying method. Nitrogen adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and thermogravimetric analysis techniques were used to characterize the materials. It was found that bimetallic nanoparticles (Ni–Ru, Fe–Ru, and Ru–Co) are homogenously dispersed in the carbon matrix and Pt nanoparticles with a size of less than 5 nm are widely distributed within the nanocomposites. The Pt/CoRuC catalyst shows better catalytic activity for the methanol oxidation reaction (MOR) than Pt on FeRuC or NiRuC, and its performance is also closer to that of the commercial PtRu catalyst with a slightly higher metal loading. A kinetic-based impedance model was used to simulate the electrochemical properties of the catalysts and matches well with the MOR performances of the catalysts. The promotional effect of the bimetallic/carbon nanocomposites on the catalytic activity of Pt was evidenced, and more importantly, the ligand effect was demonstrated by our results to be the major factor in the enhancement. Our investigation not only provides further insight into the roles of Fe, Ni and Co in MOR, but also assists in the design and synthesis of the new types of nanostructured electrocatalyst supports.

We report a facile chemical vapor deposition (CVD) method to grow silicon/carbon (Si/C) microrods on the surface of commercial graphite microspheres (GMs) to prepare Si/C/GM composite materials as Li-ion battery anodes. Dimethyldichlorosilane and toluene were used as Si and C precursors, respectively. The CVD temperature and time, as well as the mechanism of materials growth were investigated. The samples were characterized by using X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. It was found that the obtained Si/C/GM composites with an urchin-like morphology are composed of Si particles, amorphous carbon, and graphite. The CVD conditions have a significant impact on the morphology and electrochemical performance of the composite materials. The composite prepared under the optimum CVD conditions, namely at 900 °C for 5 h, displayed the best anode properties with a specific capacity of 562.0 mA h g−1 at a current density of 50 mA g−1, much higher than that of GMs (361.0 mA h g−1), and a good cycling performance (i.e., a reversible capacity of 590.5 mA h g−1 after 50 cycles). The improved electrochemical performance is attributed to the incorporation of Si, together with the formation of a Si/C microrod network, which connects the GMs and buffers the volume change of Si during lithium ion insertion/extraction. The work provides a simple and low-cost route to enhance the performance of commercial graphite anode materials for Li-ion batteries.

We report the synthesis and characterization of mesoporous cobalt ferrite (CoFe2O4, named CFO) nanospheres cross-linked by carbon nanotubes (CNTs) as anode nanocomposites (CFO/CNT) for Li-ion batteries. CFO/CNT nanocomposites were synthesized by a facile one-pot solvothermal method using Co(CH3COO)2 and FeCl3 as the metal precursors in the presence of CH3COOK, CH3COOC2H5, HOCH2CH2OH, and CNTs. The obtained samples were characterized by X-ray diffraction, thermogravimetric analysis, nitrogen adsorption, transmission electron microscopy, and scanning electron microscopy. It is found that most CFO nanospheres are interconnected with CNTs forming a network composite possibly due to the presence of defects at the open ends and on the external surface of CNTs. These defects may act as nucleation centers for growth of CFO nanospheres. Compared with the bare CFO nanospheres and the physically mixed CFO nanospheres with CNTs, the CFO/CNT composite containing 16.5 wt% CNTs shows much higher capacities of 1137.6, 1003.4, 867.3, and 621.7 mA h g−1 at the current densities of 200, 500, 1000, and 2000 mA g−1 after 10 charge–discharge cycles, respectively, and even after 100 cycles, it still maintains a high capacity of 1045.6 mA h g−1 at 200 mA g−1. The super electrochemical properties of the CFO/CNT composite should originate from the formed network structure with the intimate interconnection between CFO nanospheres and CNTs, which not only provides stable electrical and ionic transfer channels but also significantly shortens the diffusion length of the Li+ ions. This work opens a new way for fabrication and utilization of metal oxide–CNT composites as anode materials for Li-ion batteries.

A general synthetic method based on a solvothermal route for the preparation of multiple transition metal oxide (MTMO) mesoporous nanospheres (ZnaNibMncCodFe2O4, 0 ≤ a, b, c, d ≤ 1, a + b + c + d = 1) with controllable composition and uniform size distribution has been developed. The as-prepared ZnaNibMncCodFe2O4 nanospheres are formed by self-assembly of nanocrystals with the size of 5–10 nm via structure-directing agents and mineralizer coordinating effect as well as optimization of the synthesis conditions. It has been identified that the addition of mineralizer is crucial for the control of the nucleation process when the metallic precursors are reduced; meanwhile the structure-directing agent is key to forming the mesoporous structure. A number of characterization techniques including X-ray diffraction, transmission electron microscopy, scanning electron microscopy, inductively coupled plasma optical emission spectrometry, temperature-programmed reduction, and nitrogen adsorption have been used to characterize the as-prepared mesoporous products. The overall strategy in this work extends the controllable fabrication of high-quality MTMO mesoporous nanospheres with designed components and compositions, rendering these nanospheres with promising potential for various applications (oxygen reduction reaction, magnetic performance, supercapacitor, lithium-ion batteries, and catalysis).

Hierarchical dandelion-like CuO (HD–CuO) microspheres composed of nanoribbons were prepared via a facile hydrothermal method. The samples were characterized by nitrogen adsorption, X-ray diffraction, temperature-programmed reduction, thermogravimetric analysis, transmission electron microscopy and scanning electron microscopy. It was found that the reaction temperature, reaction time and reagent amounts had a significant effect on the morphology and structure of HD–CuO. The obtained HD–CuO microspheres possessed a surface area of 10.6–57.5 m2 g−1 and a diameter of 3–6 μm. In the formation process, ethylene glycol was adsorbed on the surface of the CuO nanoribbons and it acted as the structure-directing agent and thereafter the CuO nanoribbons were self-assembled into HD–CuO. The investigation of the Rochow reaction showed that the HD–CuO catalyst had a better catalytic performance in dimethyldichlorosilane synthesis than the commercial CuO microparticles and commercial CuO–Cu2O–Cu catalyst, owing to its well-developed hierarchically porous structure and higher specific surface area, leading to the increased contact interface among reaction gas, solid catalyst and solid silicon, together with enhanced mass transportation.

We report the preparation of Cu2O microparticles with different shapes, by simple hydrolyzation and reduction of copper acetate with glucose in a mixture of water–ethanol solvent. The effect of the synthesis conditions on the shape of the Cu2O microparticles and their catalytic properties in the Rochow reaction were investigated. The samples were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, temperature-programmed reduction, and thermogravimetric analysis. Cu2O microparticles with different shapes, such as hexahedron, ananas-like, sphere-like, and star-like shapes, with particle sizes of 2–4 μm, were obtained by tuning the volume ratio of water:ethanol. The hexahedron Cu2O microparticles were found to exhibit the best catalytic performance for the synthesis of dimethyldichlorosilane via the Rochow reaction. This work should be helpful in the design and development of novel copper catalysts for organosilane synthesis and understanding their catalytic roles.

A series of α-Al2O3-supported Ni catalysts with different Ni particle sizes (5–10, 10–20, and 20–35 nm) were prepared and applied in the CO methanation reaction for the production of synthetic natural gas (SNG). The catalytic tests showed that the Ni nanoparticles influenced the catalytic performance in the CO methanation, and the catalyst with a Ni nanoparticle size of 10–20 nm showed the highest CO conversion, CH4 yield, and turnover frequency, and the lowest carbon deposition, demonstrating the possibility of improving the Ni/α-Al2O3 catalysts in the CO methanation for SNG production by controlling their Ni particle size.

Nickel catalysts supported on the perovskite oxide CaTiO3 (CTO) were prepared by an impregnation method for CO methanation to produce synthetic natural gas (SNG). X-Ray diffraction, nitrogen adsorption, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, H2-temperature programmed reduction and desorption, and X-Ray photoelectron spectroscopy were employed for the characterization of samples. The results revealed that the Ni/CTO catalysts showed a better performance than Ni/Al2O3 for CO methanation at various reaction conditions. The life time test at 600 °C and 3.0 MPa indicates that Ni/CTO is also more active, thermally stable and resistant to carbon deposition. This is because of the relatively weak Ni–CTO support interaction, highly stable CTO support, the absence of acidic sites on the surface of CTO and the proper Ni particle size of about 20–30 nm. The work is important for the development of effective methanation catalysts for SNG production.

Polymer/graphene composites have attracted much attention due to their unique organic–inorganic hybrid structure and exceptional properties. In this paper, we report the synthesis of polystyrene/reduced graphene oxide (PS/r-GO) composites by a two-step in situ reduction technique, which consists of a hydrazine hydrate reduction and a subsequent thermal reduction at 200 °C for 12 h. The structure and micromorphology of PS/r-GO composites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis. The results show that the GO can be efficiently reduced by the two-step in situ reduction method, and the r-GO sheets are well dispersed and ultimately form a continuous network structure in the polymer matrix. PS/r-GO composite films (5 wt% GO) are prepared by the hot press molding method, possessing a conductivity as high as 22.68 S m−1. The superior conductivity arises from the high reduction degree of GO and its high dispersion and the formation of a network structure in the polymer matrix. These polymer/r-GO composites are expected to be applied in multiple electric devices. The techniques for preparing polymer/r-GO composite films could be further extended to other similar systems.