  A new study explores the distinct roles of spontaneous polarization and
piezoelectric polarization in piezo-phototronic coupling. This investigation
focuses on differences in photocatalytic and piezo-photocatalytic performance
using sodium bismuth titanate (NBT), a key ferroelectric material. The research
aims to identify which type of polarization has a greater influence on
piezo-phototronic effects. A theoretical assessment complements the
experimental findings, providing additional insights. This study explores the
enhanced piezo-phototronic performance of electrospun nanofibers compared to
sol-gel particles under different illumination conditions (11W UV, 250W UV, and
natural sunlight). Electrospun nanofibers exhibited a rate constant (k)
improvement of 2.5 to 3.75 times, whereas sol-gel particles showed only 1.3 to
1.4 times higher performance when ultrasonication was added to photocatalysis.
Analysis using first-principle methods revealed that nanofibers had an elastic
modulus (C33) about 2.15 times lower than sol-gel particles, indicating greater
flexibility. The elongation of lattice along z-axis in the case of nanofibers
reduced the covalency in the Bi-O and Ti-O bonds. These structural differences
led to reduced spontaneous polarization and piezoelectric stress coefficients
(e31 & e33). Despite having lower piezoelectric stress coefficients, higher
flexibility in nanofibers led to a higher piezoelectric strain coefficient,
2.66 and 1.97 times greater than sol-gel particles, respectively. This improved
the piezo-phototronic coupling for nanofibers.
