Supercritical CO ₂ ‐Dried PVA / PBI

ABSTRACT

Mechanical‐energy harvesters that retain performance under thermal and humid stress remain scarce, yet they are essential for self‐powered electronics in demanding environments. Here we report lead‐free tribo‐/piezoaerogels built from poly(vinyl alcohol) (PVA) and thermally robust polybenzimidazole (PBI), reinforced with the piezoceramic barium calcium zirconate titanate (BCZT, Ba _0.85 Ca _0.15 Zr _0.1 Ti _0.9 O ₃ ) or zinc oxide (ZnO) at 1–3 wt%. Wet gels were dried with supercritical CO ₂ (50°C, 120 bar, 60 min) to preserve a three‐dimensional macroporous network and subsequently hot‐pressed at 100°C and 0.69 MPa to enhance the output. FTIR confirmed PVA–PBI miscibility and polymer–filler interaction, FE‐SEM revealed a macroporous morphology, and TGA showed that PBI extends the major mass‐loss step to ≈480°C, far above the ≈230°C reported for glutaraldehyde‐crosslinked PVA. The thermal treatment applied to the dried aerogels reduced the internal air voids and improved interfacial and electrode contact, raising the transferred surface charge density and resulting in a remarkable up to 48‐fold increase in the power output of the nanogenerator. The highest energy‐harvesting performance was achieved with the thermally treated aerogel formulation containing 3% BCZT, exhibiting a peak‐to‐peak voltage of 19.0 V, a power output of approximately 361 μW, and a power density of approximately 180.5 μW cm ⁻² . For the 3% BCZT aerogel, the piezoelectric mechanism accounted for 85.3% of the total electrical output, while the triboelectric mechanism contributed the remaining 14.7%. Overall, this study presents a new‐generation PVA/PBI aerogel platform that combines high thermal stability, lead‐free and poling‐free operation, and enhanced electrical energy‐harvesting performance.