Molybdenum trioxide and silver hybrid nanofillers enhance the capacitance of polyvinyl alcohol and polyvinylpyrrolidone blend electrodes for supercapacitor applications

Polyvinyl alcohol/polyvinylpyrrolidone (PVA/PVP) blend nanocomposites reinforced with a hybrid MoO 3 /Ag nanofiller at 0, 1, 3, 5 and 7 wt% were prepared by solution casting and denoted PAM-x, where PAM stands for PVA/PVP–MoO 3 /Ag and x is the nanofiller content in wt%. X-ray diffraction confirmed the incorporation of both orthorhombic α-MoO 3 (JCPDS No. 05-0508) and metallic fcc Ag (JCPDS No. 04-0783) into a predominantly amorphous polymer matrix, with crystallinity increasing with nanofiller content and no secondary phases detected. SEM and TEM showed uniform dispersion of the hybrid filler in the matrix, with Ag nanoparticles (about 15–30 nm) attached to MoO₃ platelets. FTIR revealed hydrogen bonding between the polymer functional groups and MoO 3 together with the appearance of Mo–O bands, while UV–Vis spectroscopy showed enhanced visible absorption and a reduced optical band gap. Electrochemical tests were performed in a three-electrode cell in 3 M KOH over 0–0.7 V at a mass loading of 3 mg cm −2 . Cyclic voltammetry showed a transition from double-layer behaviour in the pristine blend to pseudocapacitive Mo 6+ /Mo 5+ redox behaviour in the loaded samples, and impedance spectroscopy indicated much lower series and charge-transfer resistance for PAM-5. PAM-5 delivered the highest specific capacitance of 545 F g −1 at 0.5 A g −1 , retained 485.7 F g −1 at 2.0 A g −1 (rate capability ~ 89%), and retained 79% of its initial capacitance after 1000 cycles at 2.0 A g −1 . This performance is attributed to the combined contributions of redox-active MoO 3 , conductive Ag, and the flexible PVA/PVP host. Future work will address extended cycling, post-cycling characterisation, and two-electrode device evaluation.