Synthesis of porous α-MoO3 microspheres as electrode materials for supercapacitors

•α-MoO3 microsphere was synthesized via hydrothermal reaction with aid of CrCl3.•The porous α-MoO3 exhibited high specific capacitance of 201.4 F g−1 at 0.2 A g−1.•Annealing transformed the crystal phase from hexagonal phase to orthogonal phase.•Orthogonal phase with layered structure was more beneficial to electron storage. [Display omitted] Transition metal oxides have achieved tremendous attention in the field of supercapacitor devices due to their outstanding structural properties and capacitive behavior. Herein, a porous α-MoO3 microspheres (A-SMO) were synthesized with the aid of CrCl3.6H2O via a facile hydrothermal reaction and subsequent annealing treatment. The results showed that CrCl3.6H2O plays a crucial role in manipulating morphology and increasing the specific surface area of the as-prepared products. Moreover, annealing treatment could transform the crystal structure from metastable hexagonal MoO3 to stable orthogonal MoO3, which is more beneficial for electron storage due to the layered crystal structure. Furthermore, the A-SMO displayed an excellent specific capacitance of 201.4 F g−1 compared with the pristine MoO3 (MO) of 62.0 F g−1 and the annealed MO (A-MO) of 186.5 F g−1 at 0.2 A g−1, when they were directly served as supercapacitor electrodes. This research demonstrates that the as-obtained α-MoO3 microspheres can serve as promising electrode materials for supercapacitors.