Porous ZnO-Coated Co₃O₄ Nanorod as a High-Energy-Density Supercapacitor Material

Co₃O₄ 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/Co₃O₄ heterojunction composites. Benefiting from the heterostructure to promote the charge transfer and protect Co₃O₄ from corrosion and the 1D porous structure to improve ion diffusion and prevent structural collapse in charge and discharge process, the as-prepared ZnO/Co₃O₄ composites exhibited an excellent capacitive performance and good cycling stability. The specific capacitance of the ZnO/Co₃O₄-450 (1135 F g^-1 at 1 A g^-1) was 1.4 times higher than that of Co₃O₄ (814 F g^-1), and the high-rate performance for ZnO/Co₃O₄-450 was 4.9 times better than that of Co₃O₄. Also, approximately 83% of its specific capacitance was retained after 5000 cycles at 10 A g^-1. Most importantly, the as-fabricated asymmetric supercapacitor, with a ZnO/Co₃O₄-450 positive electrode and an activated carbon negative electrode, delivered a prominent energy density of 47.7 W h kg^-1 and a high power density of 7500 W kg^-1. Thus, the ZnO/Co₃O₄ 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 Co₃O₄.