Porous ZnO-Coated CoO Nanorod as a High-Energy-Density Supercapacitor Material.

CoO with a high theoretical capacitance has been widely recognized as a promising electrode material for supercapacitor, but its poor electrical conductivity and stability limit its practical applications. Here, we developed an effective synthetic route to synthesize one-dimensional (1D) porous ZnO/CoO heterojunction composites. Benefiting from the heterostructure to promote the charge transfer and protect CoO from corrosion and the 1D porous structure to improve ion diffusion and prevent structural collapse in charge and discharge process, the as-prepared ZnO/CoO composites exhibited an excellent capacitive performance and good cycling stability. The specific capacitance of the ZnO/CoO-450 (1135 F g at 1 A g) was 1.4 times higher than that of CoO (814 F g), and the high-rate performance for ZnO/CoO-450 was 4.9 times better than that of CoO. Also, approximately 83% of its specific capacitance was retained after 5000 cycles at 10 A g. Most importantly, the as-fabricated asymmetric supercapacitor, with a ZnO/CoO-450 positive electrode and an activated carbon negative electrode, delivered a prominent energy density of 47.7 W h kg and a high power density of 7500 W kg. Thus, the ZnO/CoO composites could serve as a high-activity material for supercapacitor and the preparation method also offers an attractive strategy to enhance the capacitive performance of CoO.