The electrode material plays a crucial role in the performance of energy storage devices. Currently, the research focuses on enhancing the super-capacitive nature of the existing electrode materials in many ways. Herein, the influence of rare earth ions in the electrochemical characteristics of β-Bi2-xEuxMo2O9 and graphene-modified GrM-β-Bi2-xEuxMo2O9 is investigated. The gel matrix method is adopted for synthesizing the Bi2-xEuxMo2O9 (x = 1, 5 and 10%) and GrM - Bi2-xEuxMo2O9 (x = 5,10%). The as-synthesized material's structural formation, phase purity and structural modifications are studied using XRD, Raman and SEM. The chemical composition with their oxidation state is verified using XPS analysis. The electrochemical behavior of the pristine materials is examined with various analyses such as CV, GCD and EIS techniques in both three-electrode and two-electrode systems. The specific capacitance of GrM-Bi1.8Eu0.2Mo2O9 is 904 F g-1 at 1 A g-1 with excellent cyclic stability of about 82.14% at 5 A/g after 5000 cycles. An ASC device developed using GrM-Bi1.8Eu0.2Mo2O9 exhibits columbic efficiency of 96.5% with an extended cyclic life of 76.9% after 10000 cycles. The fabricated device possesses energy density and power density of 60.21 W h K g-1 and 750 W K g-1, respectively, at 1A g-1, acting as a favorable candidate for supercapacitor application.