Solvothermal synthesis and photocatalytic properties of NiO ultrathin nanosheets with porous structure

•Hierarchical NiO microspheres with ultrathin and porous structure were prepared by solvothermal method.•The nanoparticles were grown by the constant direction with the preferred orientation.•Structural features of NiO microspheres were characterized by means of different techniques.•High temperature annealing processing conducive to the formation of the porous feature.•NiO microspheres had better photocatalytic activity and stable cyclability for methylene blue dye under UV irradiation than commercial NiO. Hierarchical NiO microspheres, composed of ultrathin nanosheets with porous structure, are prepared through a facile solvothermal route followed by a calcination process. First, the precursor Ni3(NO3)2(OH)4 hierarchical architectures assembled by irregular nanosheets were synthesized through urea assisted precipitation. Second, the NiO hierarchical architecture was obtained from the precursor by a simple calcination procedure without changing their morphologies. The resultant products were characterized by XRD, SEM, TEM, TG, FT-IR and BET analysis techniques. The XRD pattern showed that the sample exhibited a rocksalt cubic phase structure after calcined at 500°C for 2h. The SEM and TEM images demonstrated that the as-prepared NiO were microspheres composed of ultrathin nanosheets with porous structure. The catalytic efficiency of the NiO nanomaterials is evaluated by the photocatalytic degradation of methylene blue (MB). The obtained NiO displayed the excellent degradable ability and stable cyclability to MB dye, which may be attributed to its unique hierarchical characteristics: ultrathin-porous microstructure.