Ferroelectric Polarization-Enhanced Photoelectrochemical Water Splitting in TiO₂–BaTiO₃ Core–Shell Nanowire Photoanodes

Abstract

The performances of heterojunction-based electronic devices are extremely sensitive to the interfacial electronic band structure. Here we report a largely enhanced performance of photoelectrochemical (PEC) photoanodes by ferroelectric polarization-endowed band engineering on the basis of TiO2/BaTiO3 core/shell nanowires (NWs). Through a one-step hydrothermal process, a uniform, epitaxial, and spontaneously poled barium titanate (BTO) layer was created on single crystalline TiO2 NWs. Compared to pristine TiO2 NWs, the 5 nm BTO-coated TiO2 NWs achieved 67% photocurrent density enhancement. By numerically calculating the potential distribution across the TiO2/BTO/electrolyte heterojunction and systematically investigating the light absorption, charge injection and separation properties of TiO2 and TiO2/BTO NWs, the PEC performance gain was proved to be a result of the increased charge separation efficiency induced by the ferroelectric polarization of the BTO shell. The ferroelectric polarization could be switched by external electric field poling and yielded PEC performance gain or loss based on the direction of the polarization. This study evidence that the piezotronic effect (ferroelectric or piezoelectric potential-induced band structure engineering) holds great promises in improving the performance of PEC photoelectrodes in addition to chemistry and structure optimization.

Metal–Organic Framework Derived Co3O4/TiO2/Si Heterostructured Nanorod Array Photoanodes for Efficient Photoelectrochemical Water Oxidation

“…In Figure S13 (Supporting Information), the LSV and I-t curves under chopped illumination of the photoanode are provided. [57] As for the TiO 2 /BaTiO 3 and Fe 2 O 3 /TiO 2 core/shell structures, [58,59] the photocurrent of 1.25 and 0.9 mA cm −2 at 1.23 V (vs RHE) in 1 m NaOH is reported. It is worth pointing out that the photocurrent density of the MOFs-derived Co 3 O 4 /TiO 2 /Si NR in both alkaline and neutral electrolyte, to our best of knowledge, is comparable to or even better than previously reported on the TiO 2 -based photoanodes (Table S2, Supporting Information).…”

Effect of Internal Electric Fields on Charge Carrier Dynamics in a Ferroelectric Material for Solar Energy Conversion

“…[ 5,6 ] Enhancements in device effi ciency attributed to piezoelectric or ferroelectric effects have been reported for a broad range of photovoltaic, photoelectrochemical, and photocatalytic devices. [7][8][9] The organohalide lead perovskite materials currently yielding very promising photovoltaic device effi ciencies are also reported to be ferroelectric, although the importance of their ferroelectric properties in achieving such high effi ciencies is currently unclear. [10][11][12][13] In almost all cases where enhanced solar conversion performance has been attributed to ferroelectric materials properties, this enhancement has been assigned to reduced recombination losses.…”

Computation of Electronic Energy Band Diagrams for Piezotronic Semiconductor and Electrochemical Systems

“…[27,55] All the explored variables show effects of band bending in the semiconductor within a magnitude of order (tens to hundreds of meV). As such, this charge may be of magnitudes higher than that of the piezoelectric charge density which removes the effectiveness of a piezoelectric.…”