Rare Earth Doping Engineering Tailoring Advanced Oxygen-Vacancy Co3O4 with Tunable Structures for High-Efficiency Energy Storage

Co3O4 with high theoretical capacitance is a promising electrode material for high-end energy applications, yet the unexcited bulk electrochemical activity, low conductivity, and poor kinetics of Co3O4 lead to unsatisfactory charge storage capacity. For boosting its energy storage capability, rare earth (RE)-doped Co3O4 nanostructures with abundant oxygen vacancies are constructed by simple, economical, and universal chemical precipitation. By changing different types of RE (RE = La, Yb, Y, Ce, Er, Ho, Nd, Eu) as dopants, the RE-doped Co3O4 nanostructures can be well transformed from large nanosheets to coiled tiny nanosheets and finally to ultrafine nanoparticles, meanwhile, their specific surface area, pore distribution, the ratio of Co2+/Co3+, oxygen vacancy content, crystalline phase, microstrain parameter, and the capacitance performance are regularly affected. Notably, Eu-doped Co3O4 nanoparticles with good cycle stability show a maximum specific capacitance of 1021.3 F g(-1) (90.78 mAh g(-1)) at 2 A g(-1), higher than 388 F g(-1) (34.49 mAh g(-1)) of pristine Co3O4 nanosheets. The assembling asymmetric supercapacitor delivers a high energy density of 48.23 Wh kg(-1) at high power density of 1.2 kW kg(-1). These findings denote the significance and great potential of RE-doped Co3O4 in the development of high-efficiency energy storage.