Developing a solid state electrochromic-supercapacitor prototype through DFT-guided charge transfer engineering in 2D carbon doped NiO

Abstract

Understanding the exact mechanism is the key factor for developing high-performance, application-specific devices for practical applications. Though belonging to the same family of carbon, graphene (Gr) and graphene oxide (GO) show different mechanisms of charge transport, especially in the context of their electrochemical applications. Here, the doping of carbonaceous materials (Gr and GO nano-flakes), pre-optimized using density functional theory calculations (DFT), was carried out in nanogranular NiO to design electrochromic supercapacitors. The GO-NiO electrode shows diffusion-controlled mechanism-based charge storage properties, with a high specific capacitance with sufficient color modulating properties to design a color-indicative supercapacitor. The GO-NiO electrode, when realized as an asymmetric supercapacitor (GO-NiO-SCD), displays a high capacitance value of ∼105 mF cm⁻² and 100% retention even after 500 cycles of continuous charging and discharging. The color change, coherent to (dis)charging, shows its multifunctional applications. A prototype solid state capacitor could light an LED, thus demonstrating its practical application. On the other hand, the Gr-NiO electrode demonstrated a surface-controlled mechanism, as also observed from the MEP plots of Gr and Gr-NiO, showing faster switching of less than a second to switch between colored and bleached states. This work clearly shows that tailored carbon doping in NiO unveils distinct charge storage mechanisms, empowering multifunctional devices that seamlessly merge energy storage with practical electrochromic applications, thus producing color-indicative electrochromic supercapacitors for smart building applications.