Unveiling the dynamic capacitive storage mechanism of Co3O4 @NiCo2O4 hybrid nanoelectrodes for supercapacitor applications

•Co3O4@NiCo2O4 nanoforests on Ni foam prepared by one-step solution and annealing process without using nickle source.•Synthesized electrode exhibits capacitive activation during charge-discharge cycling.•Capacitive activation is attributed to enlarged surface area and enhanced electrical conductivity.•Electrochemical induced microstructure change creates new opportunities for developing high performance energy storage materials.

We report a simple and cost-effective approach to the synthesis of hierarchical mesporous Co3O4@NiCo2O4 nanoforests on Ni foam for supercapacitor (SC) electrode applications by a coupled one-step solution and annealing process. The synthesized electrode exhibits capacitive activation during charge-discharge cycling (from 0.73 F/cm2 of the pristine state to the peak value of 1.12 F/cm2 after 2000 cycles with only 1.8% loss compared to the peak capacitance after another 2000 cycles). We attribute such dynamic capacitive activation to (1) enlarged electroactive surface area through the formation of Co3O4@NiCo2O4 core-shell structure and (2) enhanced electrical conductivity by forming oxygen vacancies and hydroxyl groups during charge-discharge cycling. Our findings provide a scientific explanation for the capacitive activation in cobalt oxide-binary nickel cobaltite compounds, and a new design guideline for the development of capacitive activation enabled, high performance transitional oxide electrodes.

Graphical abstractHierarchical mesporous Co3O4@NiCo2O4 nanoforests supported on Ni foam as supercapacitor electrodes is prepared by a coupled one-step solution and annealing process. The electrochemical performance demonstrates a dynamic capacitive storage behavior, which is attributed to enhanced electroactive surface area via forming Co3O4@NiCo2O4 core-shell structure and enhancement of electrical conductivity by forming oxygen vacancies and hydroxyl groups.Figure optionsDownload full-size imageDownload as PowerPoint slide