•Mesoporous MnO2, NiO, and Co3O4 quasi-nanospheres were prepared.•They showed the large specific surface area and narrow pore size distribution.•They demonstrated the high capacity and excellent long-term stability.In this report, we obtain mesoporous transition metal oxides quasi-nanospheres (includes MnO2, NiO, and Co3O4) by utilizing mesoporous silica nanospheres as a template for high-performance supercapacitor electrodes. All samples have a large specific surface area of approximately 254–325 m2 g−1 and a relatively narrow pore size distribution in the region of 7 nm. Utilization of a nanosized template resulted in a product with a relative uniform morphology and a small particle diameter in the region of 50–100 nm. As supercapacitor electrodes, MnO2, NiO, and Co3O4 exhibit an outstanding capacity as high as 838–1185 F g−1 at 0.5 A g−1 and a superior long-term stability with minimal loss of 3–7% after 6000 cycles at 1 A g−1. Their excellent electrochemical performances are attributed to favorable morphologies with a large surface area and a uniform architecture with abundant pores. The associated enhancement of electrolyte ion circulation within the electrode facilitates a significant increase in availability of Faradic reaction electroactive sites.

We report a facile strategy to fabricate a cadmium sulfide–ferrite (CdS–MFe2O4, M = Zn, Co) nanocomposite with differing ferrite content via a two-step hydrothermal method and demonstrate its application as a magnetically recyclable photocatalyst with enhanced visible-light-driven photocatalytic activity and photostability. The photocatalytic activities of as-prepared photocatalysts are evaluated by the degradation of rhodamine B (RhB) and 4-chlorophenol (4-CP) in aqueous solution under visible-light irradiation. Compared with pure CdS, both CdS–ZnFe2O4 and CdS–CoFe2O4 show more broad absorption in the visible-light region, which favors the visible-light utilization for better photocatalytic performance. Moreover, the surface area of cadmium sulfide–ferrite is much higher than that of pure CdS, also resulting in enhanced photocatalytic activity. Furthermore, the synergic effects of CdS and ferrites can reduce the recombination probability of photogenerated electron–hole pairs and enhance the charge separation efficiency, leading to high photocatalytic performance and remarkable inhibited photocorrosion.

A facile chemical procedure capable of aligning CuO nanoparticles on graphene oxide (GO) in a water–isopropanol system has been described. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations indicate that the exfoliated GO sheets are decorated randomly by spindly or spherical CuO nanoparticle aggregates, forming well-ordered CuO:GO nanocomposites. A formation mechanism of these interesting nanocomposites is proposed as intercalation and adsorption of Cu2+ ions onto the GO sheets, followed by the nucleation and growth of the CuO crystallites, which in return resulted in the exfoliation of GO sheets. Moreover, the obtained nanocomposites exhibit a high catalytic activity for the thermal decomposition of ammonium perchlorate (AP), due to the concerted effect of CuO and GO.

In this paper, we report a facile solvothermal route capable of aligning MnOOH nanocrystals on graphene. X-ray diffraction (XRD) and transmission electron microscopy (TEM) observations indicate that the exfoliated graphene sheets are decorated randomly by MnOOH nanocrystals, forming well-dispersed graphene–MnOOH nanocomposites. Dissolution-crystallization and oriented attachment are speculated to be the vital mechanisms in the synthetic process. The attachment of additives, such as MnOOH nanoparticles, are found to be beneficial for the exfoliation of GO as well as preventing the restack of graphene sheets. Moreover, cyclic voltammetry (CV) analyses suggest that the electrochemical reversibility is improved by anchoring MnOOH on graphene. Notably, the as-fabricated nanocomposites reveal unusual catalytic performance for the thermal decomposition of ammonium perchlorate (AP) due to the concerted effects of graphene and MnOOH. This template-free method is easy to reproduce, and the process proceeds at a low temperature and can be readily extended to prepare other graphene-based nanocomposites.Graphical abstractManganese oxyhydroxide nanocrystals have been successfully attached onto the graphene sheets via an oriented attachment and dissolution-crystallization process, forming a nanocomposite with unusual catalytic capabilities.

The well-documented novel performances of graphene make it a potential candidate for a wide range of utilizations, driving research into exploiting unusual properties of this wonder material. This paper reports a facile soft chemical approach to fabricate graphene−Co(OH)2 nanocomposites in a water−isopropanol system. Generally the depositing agent (OH−) and some reducing agents (such as HS− and H2S) could be produced from the hydrolyzation of Na2S in aqueous solution. Therefore utilizing Na2S as a precursor could enable the occurrence of the deposition of Co2+ and the deoxygenation of graphite oxide (GO) at the same time. Remarkably the electrochemical specific capacitance of the graphene−Co(OH)2 nanocomposite reaches a value as high as 972.5 F·g−1, leading to a significant improvement in relation to each individual counterpart (137.6 and 726.1 F·g−1 for graphene and Co(OH)2, respectively). The feeding ratios between Co(OH)2 and graphene oxide have a pronounced effect on their electrochemical activities.

A composite of graphene oxide supported by needle-like MnO2 nanocrystals (GO−MnO2 nanocomposites) has been fabricated through a simple soft chemical route in a water−isopropyl alcohol system. The formation mechanism of these intriguing nanocomposites investigated by transmission electron microscopy and Raman and ultraviolet−visible absorption spectroscopy is proposed as intercalation and adsorption of manganese ions onto the GO sheets, followed by the nucleation and growth of the crystal species in a double solvent system via dissolution−crystallization and oriented attachment mechanisms, which in turn results in the exfoliation of GO sheets. Interestingly, it was found that the electrochemical performance of as-prepared nanocomposites could be enhanced by the chemical interaction between GO and MnO2. This method provides a facile and straightforward approach to deposit MnO2 nanoparticles onto the graphene oxide sheets (single layer of graphite oxide) and may be readily extended to the preparation of other classes of hybrids based on GO sheets for technological applications.Keywords: capacitance; graphene oxide; hybrid material; MnO2 nanocrystals; supercapacitors