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The NiMn2O4/graphene oxide (GO) nanocomposite material was in situ grown on the surface of a nickel foam 3D skeleton by combining the solvent method with the microwave-assisted hydrothermal method and annealing; then, its performance was investigated as a superior supercapacitor electrode material. When nickel foam was soaked in GO aqueous or treated in nickel ion and manganese ion solution by the microwave-assisted hydrothermal method and annealing, gauze GO film or flower-spherical NiMn2O4 was formed on the nickel foam surface. If the two processes were combined in a different order, the final products on the nickel surface had a remarkably different morphology and phase structure. When GO film was first formed, the final products on the nickel surface were the composite of NiO and Mn3O4, while NiMn2O4/GO nanocomposite material can be obtained if NiMn2O4 was first formed (immersed in 2.5 mg/L GO solution). In a 6M KOH solution, the specific capacitance of the latter reached 700 F/g at 1 A/g which was superior to that of the former (only 35 F/g). However, the latter's specific capacitance was still inferior to that of in-situ grown NiMn2O4 on nickel foam (802 F/g). Though the gauze-formed GO film, almost covering the preformed flower-spherical NiMn2O4, can also contribute a certain specific capacitance, it also restricted the electrolyte diffusion and contact with NiMn2O4, accounting for the performance decrease of the NiMn2O4/GO nanocomposite. A convenient method was raised to fabricate the nanocomposite of carbon and double metal oxides. [ABSTRACT FROM AUTHOR]

Crystal plane engineering and defect engineering are feasible approaches to tune the electrochemical performance of nanocmaterials. Herein, a carambola-like CoWO 4 microsphere with preferred crystal planes and oxygen vacancies is synthesized by a microwave-assisted hydrothermal process together with post annealing treatment. The in-depth observation on microstructure and electrochemical tests suggest that it is the new preferred crystal planes and oxygen vacancies in CoWO 4 that improves conductivity and reaction activity to lead to a much higher capacity. Further density functional theory (DFT) analysis reveals that tuning the preferred crystal plane and introduction of oxygen vacancy into CoWO 4 not only effectively enhance electronic conductivity, but also promote OH− adsorption/desorption, and reduce electronic transmission barrier. As a result, the as-obtained carambola-like CoWO 4 microsphere with preferred crystal planes and oxygen vacancies delivers high specific capacity (493.7 C g−1/137.1 mA h g−1 at 1 A g−1) with superior rate capability (148.6 C g−1/41.3 mA h g−1 at 15 A g−1). Moreover, the cycling-induced morphology evolution lead to unconventional capacity increasing during cycling. The as-fabricated A-CoWO 4 //6 M KOH//activated carbon (AC) BSH device exhibits a maximum energy density of 27.5 Wh kg−1 at 1031.4 W kg−1 and 95.7% capacity retention after 12000 cycles. This work provides a possible way to improve the electrochemical performances of other metal oxide electrodes with low-capacity and irreversibility. [Display omitted] • ●CoWO 4 with preferred crystal planes and oxygen vacancies was synthesized. • ●A-CoWO 4 electrode exhibits improved conductivity and reaction activity. • ●DFT reveals the effect of preferred orientation and oxygen vacancies. • ●The morphology remolding lead to an increased cycling capacity phenomenon. • ●BSH devices deliver 27.5 Wh kg−1 energy density at a power density of 1031.4 W kg−1 [ABSTRACT FROM AUTHOR]

The α-MoO 3 -based materials have been intensively investigated as chemiresistive-type gas sensors due to their excellent sensing performances for gas sensing applications. However, there still remains formidable challenges for developing a simple and scalable approach to synthesize α-MoO 3 with controllable structures. Herein, we demonstrated a glucose-assisted combustion synthesis strategy for the synthesis of α-MoO 3 materials with controllable structures. They were obtained by heat treatment of the gels containing ammonium heptamolybdate tetrahydrate and glucose. Owing to the coordination interactions between glucose and heptamolybdate, α-MoO 3 -2 sample obtained by adding 1.8 g of glucose featured the highest oxygen vacancy concentration with an O/Mo atomic ratio of 2.61. The gas sensing measurements indicated that α-MoO 3 -2 had excellent sensing performances for detecting ethanol. Such ethanol sensor displayed the lowest detection concentration of 5 ppm ethanol, high response of 3.86 toward 20 ppm ethanol, and wide detection range of 5–100 ppm. This study sheds light on preparation of metal oxides with controllable structures on a scalable way for various applications. • A glucose-assisted combustion synthesis method have been developed to preparation of MoO3 samples. • The MoO3 sample thus obtained possesses high oxygen vacancy concentration and surface chemical-adsorbed oxygen species. • The MoO3 sample exhibits excellent sensing performances for ethanol sensing. [ABSTRACT FROM AUTHOR]