Effect of grain size on electrochemical performance and kinetics of Co3O4 electrode materials

Abstract

Co₃O₄ has attracted extensive attention as an electrode material for pseudocapacitors due to its simple preparation process and high theoretical capacity (3560 F g⁻¹). Although the experimental specific capacitance is much lower than its theoretical value, in-depth research into its kinetics, which is urgently needed for further performance improvement, is still rarely seen. Here, Co₃O₄ electrodes with the same morphology but different grain sizes are prepared. The kinetic connection between grain size and electrochemical performance is investigated. It can be found that a smaller Co₃O₄ grain size is beneficial for immersion in the electrolyte, which can enhance the diffusive capacity. Furthermore, for the first time, using distribution of relaxation times (DRT) calculation, the relationship between the grain size and the reaction activation energy is studied. The results demonstrate that Co₃O₄ with a small grain size has a low activation energy of the charge transfer reaction and diffusion, which will make the redox reaction and diffusion in the Co₃O₄ electrode easier, thus leading to the improvement of the electrochemical performance.