•Controllable preparation of nano-TiO2 is achieved by a solvothermal method.•TiO2 morphology is tailored by tuning reactant ratio, temperature and duration.•Needle structured TiO2 shows enhanced lithium storage capability.Facile and controllable preparation of TiO2 is of prime importance to elaborately tailor and then fully exploit its intriguing functionalities in energy storage, catalysis and environmental remediation. Herein, a solvothermal method combined with post annealing is conducted, in which the hydrolysis of tetrabutyl titanate is controlled by the in-situ generated water during solvothermal treatment. By controlling synthetic conditions (i.e. reactant ratio, solvothermal temperature and reaction time), we manage to tailor the morphologies of TiO2. Specially, three typical structures (nanoparticle, nanoneedle and nanorod) are studied to reveal the growth mechanism and the effects of the synthesis conditions. Nanoneedle-structured TiO2 shows higher specific capacity and enhanced cycle stability as anode material for lithium ion batteries.

•The spheres are rationally designed and synthesized via a facile solution-based method.•The as-prepared spheres exhibit high surface area and excellent structural stability.•The spheres demonstrate significantly enhanced electrochemical performance for supercapacitors.UltrathinCo9S8nanosheets were successfully assembled into a carbon supported nanostructure of C@Co9S8core-shell hollow spheres by a facile solution-based method consisting of template-engaged growth of a precursor shell, followed by simultaneous sulfidation and removal of template. The prepared C@Co9S8hollow spheres exhibit enhanced electrochemical performance in supercapacitors due to their high surface area and excellent structural stability.Carbon supported Co9S8hollow spheres (C@Co9S8) assembled from ultrathin nanosheets are prepared via a facile solution-based approach including the template-engaged growth of precursor shell followed by simultaneous sulfidation and template removal. The as-fabricated hierarchical hollow spheres possesses a high specific surface area (266 m2 g−1) with good structural stability, and exhibit high specific capacitance with excellent cycling performance as electrode materials for supercapacitors.

TiO2 nanoparticles with a specific surface area of ~200 m2 g−1 were successfully fabricated by a facile hydrothermal method using Ti(OC4H9)4 as the precursor at 180 °C for 24 h. The as-prepared sample was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–teller (BET) surface area, and UV–vis diffuse reflectance spectrum. The photocatalytic activity of the as-prepared sample was evaluated by photocatalytic degradation of gaseous benzene. The results show that TiO2 nanoparticles exhibit much better photocatalytic activity towards the photodegradation of benzene than Degussa P25. The good photocatalytic activity of TiO2 nanoparticles is attributed to the large specific surface area and high separation efficiency of photogenerated electrons and holes.

Implementation of non-precious electrocatalysts towards the oxygen reduction reaction (ORR) is the central focus for fulfilling cost-affordable and high-performance fuel cells and metal/air batteries. Herein, we report a modified solvothermal approach for the preparation of composite carbonates between Mn and X (X = Co, Ni and Fe). Upon post-annealing treatment, the aforementioned carbonates are transformed into the corresponding micro/nano hierarchical structured mixed oxides with increased porosity. It is found that onion-like core–shell architectures appear in the Mn–Co and Mn–Ni systems because of volume shrinkage arising from the generation of chemical-level mixed oxides, while a less porous structure occurs in the Mn–Fe system with the formation of a physical-level mixture. The ORR activity of the prepared composite oxides in alkaline media is investigated by voltammetry under different hydrodynamic conditions. An enhanced ORR activity is observed in the Mn–Co mixed oxide, which is rationalized in terms of the unique microstructure and crystallographic phase. The present study suggests that proper mixing is an effective method for activating the ORR activity of manganese oxides, which is beneficial for developing non-precious electrocatalysts for fuel cells and metal/air batteries.

A novel two-step synthetic strategy was proposed to synthesize urchin-like nickel cobaltite (NiCo2O4) microspherical hierarchical superstructures constructed by one-dimension nanowires: hydrothermal precipitating (Ni, Co) carbonate hydroxide followed by calcinating process. Electrochemical data reveals that the as-synthesized urchin-like NiCo2O4 superstructures can deliver a specific capacitance (SC) of 296 F/g at 1 A/g, and keep it as high as 215 F/g at 5 A/g in 6 M KOH aqueous solution. Such unique urchin-like hierarchical superstructures make each electroactive NiCo2O4 nanowire building block contacted easily by electrolyte ions and electrons at high rates, ensuring that sufficient Faradaic reactions take place at large current densities for energy storage. Moreover, no obvious SC degradation after 1000 continuous charge–discharge cycles at 2 A/g demonstrates good electrochemical stability of the urchin-like microspherical superstructures, promising their great potential application in electrochemical capacitors.

A facile one-pot hydrothermal strategy was proposed to prepare ultrathin α-Co(OH)2 nanosheets with a thickness of ca. 10 nm. Electrochemical data demonstrated that the ultrathin Co(OH)2 nanosheets delivered a specific capacitance of 401 F g−1 at a current density of 0.67 A g−1, and even 232 F g−1 at 10 A g−1. A specific capacitance degradation is ca. 2% after 1000 continuous cycling at 4 A g-1. The desirable electrochemical performance of the ultrathin nanosheets mainly stems from the large interfacial area of solid/liquid reaction due to their large interlayer spacing and ultrathin nature, indicating that the ultrathin α-Co(OH)2 nanosheets are a good candidate for electrochemical capacitor application.Highlights► Ultrathin α-Co(OH)2 nanosheets were prepared by one-pot strategy. ► Large interlayer spacing of the ultrathin NiO nanosheets. ► Ultrathin structure enhances its electrochemical utilization. ► A specific capacitance of 401 F g−1 is delivered at 0.67 A g−1.

Implementation of non-precious electrocatalysts towards the oxygen reduction reaction (ORR) is the central focus for fulfilling cost-affordable and high-performance fuel cells and metal/air batteries. Herein, we report a modified solvothermal approach for the preparation of composite carbonates between Mn and X (X = Co, Ni and Fe). Upon post-annealing treatment, the aforementioned carbonates are transformed into the corresponding micro/nano hierarchical structured mixed oxides with increased porosity. It is found that onion-like core–shell architectures appear in the Mn–Co and Mn–Ni systems because of volume shrinkage arising from the generation of chemical-level mixed oxides, while a less porous structure occurs in the Mn–Fe system with the formation of a physical-level mixture. The ORR activity of the prepared composite oxides in alkaline media is investigated by voltammetry under different hydrodynamic conditions. An enhanced ORR activity is observed in the Mn–Co mixed oxide, which is rationalized in terms of the unique microstructure and crystallographic phase. The present study suggests that proper mixing is an effective method for activating the ORR activity of manganese oxides, which is beneficial for developing non-precious electrocatalysts for fuel cells and metal/air batteries.