The built-in electric field induced by piezoelectric
polarization
is an important method to effectively improve the inefficient charge
transport of photoelectrochemical (PEC) water splitting. Here, we
introduce a certain amount of W5+ into Bi2WO6 crystal to modulate its piezoelectric polarization performance,
thus improving its piezoelectric internal electric field to drive
the separation of carriers to improve the piezoelectric photoelectrochemical
(piezo-PEC) water splitting. The doping of W5+ ion widens
the visible light response of the sample on the one hand, and increases
the free charge density in Bi2WO6 nanosheets
on the other hand, thereby improving the charge transfer efficiency.
The Bi2WO6-2 sample exhibits the best photochemical
properties, and the photocurrent density was 0.126 mA/cm2 at 1.23 V vs RHE. In addition, under ultrasonic conditions, the
current of the Bi2WO6-2 photoelectrode was enhanced
to 0.181 mA/cm2 at 1.23 V vs RHE. The effect of ion doping
on piezo-PEC performance was further explained by comparing the PEC
performance of the samples before and after the introduction of the
piezoelectric built-in electric field. This work suggests future uses
for Bi2WO6 piezo-PEC water splitting.
The lower polarization intensity and charge separation efficiency are the main factors hindering the wide application of piezoelectric photoelectrocatalytic (piezo-PEC) water splitting. Here, we first introduced lattice fluorine into the bulk Bi 2 WO 6 by fluorination treatment to improve the piezoelectric polarization intensity of Bi 2 WO 6 . In addition, the adsorbed fluorine produced by the fluorination treatment can promote the effective separation of the surface photogenerated charges, thus achieving the effective transfer and separation of the bulk and surface photogenerated charges, further realizing the efficient piezo-PEC water splitting performance. The photocurrent of Bi 2 WO 6 with lattice fluorine and adsorbed fluorine reaches 0.298 mA/cm 2 under ultrasonication by proper fluorination, which is almost 3.3 times that of pure Bi 2 WO 6 under the same conditions. Detailed experimental data shows that the presence of lattice fluorine and adsorbed fluorine can not only effectively improve the bulk piezoelectric polarization of the photoelectric electrode but also effectively optimize the surface photoinduced charge separation. This study provides a promising approach to improve the performance of piezo-PEC by tuning the polarization intensity and surface state of the piezoelectric material.
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