Morphological and structural aspects in <scp>PVDF</scp> / <scp> CoFe ₂ O ₄ </scp> membranes and their influence on piezocatalytic activity

Abstract This study explores the structural, morphological, optical, dielectric, piezoelectric, and piezocatalytic properties of polyvinylidene fluoride (PVDF) composite membranes incorporating cobalt ferrite (CoFe 2 O 4 , CFO) nanoparticles at 25 and 35 wt% loadings. X‐ray diffraction (XRD) and Fourier‐transform infrared spectroscopy (FTIR) confirmed the retention of electroactive β‐ and γ‐phases, with the PVDF matrix maintaining approximately 50% crystallinity. Morphological analysis demonstrated reduced porosity, increased surface roughness (Rq increased from 155 to 442 nm for PVDF/CFO10), and nanoparticle aggregation with higher CFO content. Optical studies revealed a significant reduction in reflectance and increased absorption due to CFO incorporation. Piezoelectric force microscopy (PFM) confirmed enhanced local electromechanical response, with a 20% increase in active piezoresponse areas under an external magnetic field. Dielectric analysis demonstrated frequency‐dependent permittivity changes, with a notable increase in ε ′ under mechanical load. The piezoelectric coefficient d₃₃ increased from 3.5 pC/N in pure PVDF to 9.1 pC/N for PVDF/CFO10. Under ultrasonic excitation, PVDF/CFO10 achieved 84% methylene blue degradation, attributed to cavitation centers formed by surface‐exposed CFO nanoparticles. Piezoelectric nanogenerators (PENGs) based on PVDF/CFO10 generated a maximum open‐circuit voltage of 17.6 V under vertical compression and ±2 V under ultrasonic stimulation. These findings highlight the multifunctionality of PVDF/CFO composites for energy harvesting, dielectric applications, and environmental remediation. Highlights Cobalt ferrite CoFe 2 O 4 (CFO) nanoparticles improve polyvinylidene fluoride (PVDF) piezocatalysis, achieving 84% methylene blue degradation. Approximately 10% CFO content enhances membrane surface activity and cavitation effects. PVDF/CFO composites retain approximately 50% crystallinity with β‐ and γ‐phase stability The piezoelectric coefficient d₃₃ increased from 3.5 pC/N (PVDF) to 9.1 pC/N (PVDF/CFO10). ±2 and 17.6 V output voltage achieved under ultrasonic excitation and under mechanical compression in PVDF/CFO10 membranes. Composite membranes offer dual functionality for energy and environmental uses.