Porous tricobalt tetraoxide (Co₃O₄) nanoplates with large aspect ratio have been obtained by annealing Co(OH)₂ precursor nanoplates synthesized by a facile reflux method without the need for any template or surfactant. After the heat treatment, the as-obtained phase-pure Co₃O₄ nanoplates with a wellretained structure were applied as the electrode material for supercapacitors, and the sample exhibits excellent performance with a high specific capacitance of 225 F g^–1 after 2000 charge–discharge cycles at 2 A g^–1, corresponding to a retention of 97% of the initial capacitance.

Co$_9$S$_8$ nanotubes have been successfully synthesized via a facile two-step solvothermal method without the assistance of any template or surfactant, using cobalt sulphate (CoSO$_4$·7H$_2$O), urea and sodium sulphide (Na$_2$S·9H$_2$O) as starting reactants, and deionized water and glycol as the reactive medium. The phase and the morphologyof the as-obtained product were characterized by means of powder X-ray diffraction, energy dispersive spectrometry and scanning electron microscopy. The result displays that the Co9S8 nanotubes have hexagonal crosssections,the diameter of the nanotubes is about 200 nm and the wall thickness is of 50 nm. The experiments showed that the Co$_9$S$_8$ nanotubes could be used as new-type catalysts for the reduction of 4-nitrophenol. It was found thatthe as-obtained Co$_9$S$_8$ nanotubes contributed to the best catalytic activity.

Monodispersed Co$_3$O$_4$ nanocubes were prepared by a simple hydrothermal route with sodium pentanesulphonate,employing Co(NO$_3$)$_2$·6H$_2$O and NH$_3$·H$_2$O (28 wt%) as the starting reactants.The final product was characterizedby powder X-ray diffraction, energy-dispersive X-ray spectrometry, scanning electron microscopy and transmission electronmicroscopy. The as-prepared Co3O4 nanocubes could photocatalytically degrade organic dye Rhodamine B under irradiation of 365 nm ultraviolet light.