Internal‐Field‐Enhanced Charge Separation in a Single‐Domain Ferroelectric PbTiO₃ Photocatalyst

Abstract

Ferroelectric materials with spontaneous polarization‐induced internal electric fields have drawn increasing attention in solar fuel production due to the intrinsic polarized structure. However, the origination of charge separation in these materials at the nano/microlevel is ambiguous owing to the complexity of the multielectric fields. Besides, the observed charge separation ability is far from theoretical expectation. Herein, by spatially resolved surface photovoltage spectroscopy, it is clearly demonstrated that the depolarization field in single‐domain ferroelectric PbTiO3 (PTO) nanoplates is the main driving force for charge separation and it can effectively drive photogenerated electrons and holes to the positive and negative polarization facets, respectively. Moreover, the charge separation ability of PTO nanoplates increases with increasing particle size along the polarization direction, due to the increasing potential difference between the opposite polarization facets. Furthermore, this driving force for charge separation directly contributes to the enhancement of the photocatalytic hydrogen evolution reaction activity in ferroelectrics. Finally, it is proved that the screening field compensates part of the depolarization field and can be diminished by adding a dielectric layer on the ferroelectric surface. These findings demonstrate the importance of increasing the depolarization field and decreasing the screening field for efficient charge separation in ferroelectric semiconductor photocatalysts.

Reactive Oxygenated Species Generated on Iodide‐Doped BiVO4/BaTiO3 Heterostructures with Ag/Cu Nanoparticles by Coupled Piezophototronic Effect and Plasmonic Excitation

“…[ 51 ] Surprisingly, the saturation polarizations of BiVO 4 /BTO and BiVO 4 :I/BTO supported with PVDF thin films were between those observed for BiVO 4 and BTO supported with PVDF thin films, implying that BiVO 4 /BTO and BiVO 4 :I/BTO heterostructures possessed defined polarization fields, which can act as driving forces to accelerate the separation and transportation of photoexcited charge carriers. [ 29b,52 ] However, the saturation polarizations in the PVDF thin films of BiVO 4 :I/BTO‐Ag and BiVO 4 :I/BTO‐Cu deteriorated rapidly, because the finite Ag and Cu nanoparticles improved on the conductivity. Nevertheless, this phenomenon did not mean that BiVO 4 :I/BTO‐Ag and BiVO 4 :I/BTO‐Cu had poor abilities for separating charge carriers, this occurred because BiVO 4 :I/BTO acted as a carrier for the loaded plasmonic metal nanoparticles and could in addition be used to control the transfer of plasma‐induced charges.…”

Strain‐Engineered Nano‐Ferroelectrics for High‐Efficiency Piezocatalytic Overall Water Splitting

“…Figure 4 e,f and Figure S14 show that the as‐grown b ‐BaTiO 3 nanoparticle exhibits an asymmetric hysteresis behavior in dark, which is attributed to the built‐in field associated with the energy band bending. It is well known that this internal electric field mainly originates from the polarization‐induced depolarization field, driving the photoinduced charge separation [29] . After the 400 nm light irradiation, the photoinduced charges are adsorbed onto the polar surface of b ‐BaTiO 3 and drive away the previously absorbed screening charges, i.e., H + /OH − [30] .…”

Synergy of ferroelectric polarization and oxygen vacancy to promote CO2 photoreduction

“…On the other hand, Li et al revealed that the depolarization field a driving force to disperse photogenerated electrons and holes to the opposite polarization facets in single-domain ferroelectric PbTiO 3 nanoplates. Notably, the depolarization field can be directly increased with the increasing particle size along the polarization direction, further improving the photocatalytic hydrogen evolution reaction activity 22 . Despite the promising results obtained with polarized semiconductors, efforts in understanding and further development of this approach are mainly restricted in thin-film photoelectrodes.…”