Rapid fabrication of morphology-controlled nano-flower Co3O4(OV) from CoAl intermetallic via thermal explosion combined with dealloying for self-supported supercapacitor electrodes

Abstract

Chemical/electrochemical dealloying was applied to porous CoAl intermetallic (IMC) precursors synthesized via a rapid thermal explosion (TE) method, producing Co3O4(OV) self-supported materials with rod-like, nano-flower, and honeycomb-like nanostructures. The investigation thoroughly explored the phase composition, exothermic behavior, precursor morphology, electrochemical characteristics of the dealloyed products, and the mechanism of oxygen vacancies that influence the performance of supercapacitors. The diffusion of intermediate phases governs the exothermic behavior and structural integrity of the CoAl IMC precursors, formatting a precursor with a porous material featuring a 3D microstructure. The effect of dealloying time, temperature and, applied potential on the nanostructure of the sample was examined, ultimately enabling the controlled synthesis of nano-flower Co3O4(OV) in the dealloying process. The synthesized self-supported Co3O4(OV) materials with a relatively high concentration of oxygen vacancies and a high specific surface area (36.69 m²/g). The materials showed high capacitance (11.25 F/cm2 at 10 mA/cm2) and exceptional cyclic stability (the decay rate per cycle is 0.013 % at 20 mA/cm2 after 2000 cycles). DFT simulations demonstrated that the OV creates additional unsaturated coordination sites, enhancing the storage capacity by facilitating ion insertion and extraction, thus significantly boosting the specific capacity.