Impact of annealing on Cu2O doped with Na/Co: Structural, optical, and electrochemical consequences

Abstract

The Na and Co doped Cu2O were synthesized by the sol–gel method and annealed at different temperatures under ambient conditions. This study systematically investigated the impact of annealing on the structural, optical, and electrochemical characteristics. The X-ray diffraction pattern reveals the formation of Cu2O with a partial presence of CuO. After the annealing process, the majority of the phases underwent a conversion to CuO, along with a partial amount of Cu2O, Cu(OH)2, and Cu, as determined by XRD and Raman analysis. The current–voltage relationship revealed an increase in conductivity, which was associated with oxygen vacancy, as the annealing temperature rose. The material's band gap was found to be suitable for its application in optoelectronic devices. Additionally, the specific capacitance gradually increased with the rise in annealing temperature. The electrode using Na and Co-doped Cu2O annealed at 800 °C (Cu-800) showed a capacitive retention of 80.1 % after 500 cycles. The particle size, pore size, and specific surface area were examined using FESEM and BET characterization, respectively. The XPS spectra clearly indicated the presence of copper and cobalt with multiple oxidation states and sodium with single oxidation states. Finally, the photoluminescence (PL) spectra showed an increase in oxygen vacancies with the incorporation of annealing temperature, which is an important attribute for the material's suitability for photoenergy conversion and energy storage applications.