Coating titanium oxide nanorods with barium strontium titanate shells boosts water splitting

As ferroelectric materials become increasingly investigated for photoelectrochemical uses, titanium oxide-based ferroelectrics received widespread attention in water splitting research. It is believed the material’s spontaneous polarization, inducing an unscreened field, assists charge separation and promotes energy conversion. The use of such materials in nanoscale heterostructures, however, continues to be hampered by size effects.

Wang et al. report a method for further boosting the conversion efficiency of titanium oxide nanorods. By coating titanium oxide nanorods with a ferroelectric shell layer composed barium strontium titanate with ferroelectric instability, the group found unexpectedly improved photoelectrochemical water splitting.

The results provide new insight into how the integration of ferroelectric materials, particularly the influence of dynamic polar order engineering on the photocarrier transport kinetics, may help to promoting the carrier kinetics in solar energy conversion.

“The hydrothermal conversion technique is not something completely new,” said author Lu You. “However, the physical mechanism we proposed to explain the enhanced performance of the rod-shell nanostructure is innovative.”

The group proposes the enhanced electrical susceptibility due to ferroelectric instability facilitates the formation of ferroelectric polarons that protect the photocarrier transport from adverse recombinations with charge defects and opposite carriers.

The resulting decrease in recombination leads to increased carrier lifetime and cell efficiency.

“Destabilizing the ferroelectricity may not be a bad thing,” You said. “In turn, it increases the electric susceptibility, which is beneficial in protecting the photocarrier from recombination loss.”

The group hopes the work contributes to the field’s understanding of polaron formation and looks to probe transient photoexcited carrier kinetics of the nanostructured samples with ultrafast spectroscopy.

Source: “Understanding improved photoelectrochemical performance in Ba_xSr_1-xTiO₃/TiO₂ rod-shell nanostructures,” by Wei Wang, Yuyan Weng, Baoxing Tu, Yang Zhou, Fengang Zheng, Liang Fang, and Lu You, AIP Advances (2021). The article can be accessed at https://doi.org/10.1063/5.0062958 .