Engineering CaO@activated carbon nanocomposite for simultaneous energy storage and pollutant adsorption

A nanoconfinement approach was employed in this study to encapsulate activated carbon with calcium oxide NPs. Here, we present an innovation in materials science by introducing a CaO@AC bifunctional catalyst with unique crystallographic structure and outstanding properties for wastewater treatment and energy storage. This catalyst enables the fast degradation of cocktail pollutants within a minimum time and is useful for the storage of clean energy. The photocatalytic degradation of rhodamine-B, rose bengal, and methylene blue was successfully performed by the bifunctional catalyst with 95%, 74%, 86% degradation efficiencies, respectively, within 40 min. The bifunctional catalyst showed a low charge transfer resistance, decreasing from 1.81 Ω before charge-discharge cycling to 1.62 Ω after cycling, indicating faster ionic diffusion, higher structural stability, and increased surface activation of the electrode. This catalyst achieved a high specific capacity of 230 F g^-1 at 4 A g^-1 in 3 M KOH and retained approximately 99% of its initial capacitance after 5000 cycles. Additionally, the doped CaO@AC nanocomposite exhibited an enlarged CV area compared with the AC electrode, indicating an enhanced electron adsorption capacity due to the surface functionalities of the CaO@AC matrix. This work paves the way for the further exploration of the innovative CaO@AC bifunctional catalyst as a promising candidate for sustainable development.