Enhancing CeO 2 Thin Films with Mo Doping for High‐Performance Supercapacitors

This study presents the development of molybdenum‐doped cerium oxide (Ce 1− x Mo x O 2 ) thin‐film electrodes for electrochemical energy storage, synthesized via the spray pyrolysis method. Molybdenum doping induces oxygen vacancies (V o ) in the CeO 2 structure, significantly enhancing its charge storage capacity. Structural analysis using X‐ray diffraction and Raman spectroscopy confirmed a polycrystalline fluorite‐type structure with decreasing crystallite size as Mo content increased. The Raman peak at 461 cm −1 shifted to lower frequencies, and a broad band between 540 and 630 cm −1 , indicative of oxygen vacancies, intensified with doping. Scanning electron microscopy‐energy‐dispersive X‐ray spectroscopy analysis showed good film adhesion, smooth surface morphology, and minimal oxygen deficiency. Optical studies revealed that Mo doping decreased film transmittance (60–80%) and reduced the optical bandgap from 3.28 eV (undoped) to 2.89 eV (6% Mo). Electrochemical performance, evaluated by cyclic voltammetry, demonstrated improved specific capacitance due to increased Ce 3+ /V o sites. The best performance was achieved at 6 at% Mo doping, with a specific capacitance of 209.16 F g −1 at 20 mV s −1 and 302.55 F g −1 at 0.5 A g −1 . The electrode also exhibited excellent cycling stability, with only 2.73% capacitance loss after 1000 cycles.