Porous CoO/carbon foam composites synthesized by solvothermal method for supercapacitor and enhanced microwave absorption applications

Composite materials comprising porous carbon foam and transition metal oxides exhibit significant potential for applications as supercapacitor electrodes and electromagnetic microwave absorbers. In this work, N-doped three-dimensional carbon foam was obtained by carbonizing melamine foam, and subsequently, a solvothermal method was used to construct a 0D/3D structure by integrating CoO nanoparticles with the three-dimensional carbon foam. The carbon foam serves dual purpose as a growth substrate and a conductive framework, effectively enhancing the electronic conductivity between the components and mitigating issues related to CoO nanoparticle aggregation. Due to the synergistic effect of pseudocapacitance and double-layer capacitance, CoO/CF exhibits enhanced supercapacitor performance, demonstrating an outstanding specific capacitance of 221 F g−1 at 1 A g−1, and surpassing that of individual component. The assembled asymmetric supercapacitor achieves a satisfactory energy density of 28.8 Wh kg−1 at a power density of 804.3 W kg−1, and retains 80.3 % of its initial capacitance after 5000 cycles at 10 A g−1. Furthermore, the microstructure was designed by the combination of carbon foam's excellent dielectric loss and CoO's magnetic loss compensating for the magnetic loss deficiency of carbon foam, thereby significantly enhancing the composite's capacity for electromagnetic wave absorption. At a thickness of 3 mm, the composite attains a minimum RL value of −14.1 dB at 14 GHz, with an effective absorption frequency width of 2.1 GHz. This well-designed and adjustable composite strategy holds great promise for applications in the fields of supercapacitors and microwave absorption.