Structural, morphological, optical, and electrochemical properties of Zn-doped CeO2/rGO nanocomposites

Abstract

Metal-doped cerium oxide has recently attracted the interest of researchers worldwide because of its various applications in different fields such as supercapacitors, high-sensitivity electrodes or photocatalytic. Metal-doped cerium oxide can be improved utilizing a variety of metals and composites with enhanced conductivity, which advances materials science in semiconductor processing. In this study, undoped and Zn-doped CeO₂ nanoparticles at 5, 10, 15, and 20 at.% were reacted with reduced graphene oxide (rGO) using a hydrothermal method. They were heated at 150 °C for 12 h and then processed in an ultrasonic reactor (20 kHz) at 25 ± 1 °C. Their structural, morphological, elemental, optical, and electrochemical properties were systematically characterized. The calculated average crystallite sizes of CeO₂ peaks ranged from 4.60 ± 0.2 to 12.0 ± 0.4 nm. These samples exhibited a single CeO₂ phase corresponding to a face-centered cubic structure, except for 20 at.% Zn-doped CeO₂/rGO, which presented a ZnO phase. The samples had lower band gap values than expected for undoped CeO₂ nanoparticles, higher valence states due to their Ce³⁺/Ce⁴⁺ ratios, and a large surface area, 242 m²/g, due to Zn-doping in CeO₂ samples. The highest specific capacitance values achieved were 88.49 F/g at 5 mV/s and 134.01 F/g at 0.5 A/g for undoped CeO₂/rGO. Zn-doping resulted in decreased capacitive behavior with specific capacitance values in the range of 70.78–81.00 F/g at 5 mV/s and 79.24–101.43 F/g at 0.5 A/g. This study for synthesizing Zn/CeO₂/rGO ternary nanocomposites produced materials with improved band gaps, valence states of Ce³⁺/Ce⁴⁺ ratios, and greater surface area for improved electrocatalytic performance.