PbTiO₃ Based Single-Domain Ferroelectric Photocatalysts for Water Splitting

Abstract

Metrics & MoreArticle Recommendations CONSPECTUS: Solar-driven photocatalytic water splitting paves a way to produce green hydrogen for building a sustainable clean energy system, particularly within the framework of the carbon-neutral initiative. However, to date, the solar-to-hydrogen (STH) conversion efficiency of particulate photocatalysts falls far short of the demand of over 10% for industrial applications. Single-domain ferroelectric semiconductor materials with amazing unidirectional spontaneous polarization penetrating the bulk are promising candidates as photocatalysts for water splitting. Their existing inherent internal field set up by polarization can cause both two oppositely charged surfaces (namely, polar surfaces) and spatial separation of photogenerated charge carriers between them upon light excitation. These unique properties provide sufficient new room for flexibly engineering of bulk and surface/interface structures to enhance photocatalytic water splitting.In this Account, we offer a systematic overview of the exploration of PbTiO 3 based singledomain ferroelectric photocatalysts for efficient solar water splitting. In detail, the controlled growth, surface modification, heterostructures, and Z-scheme system of single-domain PbTiO 3 ferroelectrics are discussed by considering polar surfaces, spatial separation of the photoexcited charges, selective distribution of defects, and selective adsorption of reactive species. We start with the controlled synthesis of single-domain ferroelectric PbTiO 3 nanoplates to realize the opposite directional transport of photoexcited charges driven by the polarized internal electric field, which can be verified by the fact that photochemical reduction/oxidation deposits occur on opposite polar surfaces. Then, we move to the selective modification of the specific polar surface to promote the transfer of photoexcited charges by applying the spatial separation effect of photoexcited charges and defects related internal screening mechanism. Furthermore, asymmetric heterostructures and Z-scheme systems are rationally designed by selective adsorption of reactive species on charged surfaces to promote charge separation and suppress redox mediator side reactions, respectively. Although significant advances have been achieved, many efforts remain needed toward the industrial production target. Based on single-domain ferroelectric photocatalysts, we present the following perspectives on the utilization of a wide solar spectrum for improving solar energy conversion efficiency. First, proper dopants can be incorporated homogeneously in the bulk to reduce the bandgap without obviously weakening ferroelectricity. Second, the epitaxial growth of narrow bandgap semiconductors on the ferroelectrics is feasible to induce additional polarization in the region close to their interface. These two aspects are anticipated to enable strong visible light absorption and charge separation efficiency. Third but not least, the assembly of Z-scheme systems with two narrow bandgap ferroel...

The Ferroelectric Effects of Rhombohedral and Tetragonal BiFeO3 in Photoelectrochemical Water Splitting

“…In ferroelectrics, the depolarization field generated by the screening effect of the bound charges is mainly responsible for charge separation . In the case of T-BFO, however, the bound charges of the film lead to a strong Coulomb interaction with the photogenerated electrons accumulated at the surface. , Consequently, the bound charges of the T-BFO film will hamper the transfer of the photogenerated electrons from the surface of the films to the electrolyte . Next, we further examined the charge injection efficiency, which is defined as the yield of electrons that are injected into the electrolyte to reduce protons .…”

Na/Mo co-doped PbTiO3 for photocatalytic water oxidation and Z-scheme overall water splitting under visible light

“…4 In recent years, ferroelectric semiconductors have demonstrated great potential in photocatalytic solar energy to hydrogen conversion, 5,6 where the built-in electric field in materials could facilitate the separation and transport of the photogenerated carriers and thus high photocatalytic capacities. The wide band gap ferroelectric photocatalysts explored exhibit excellent photocatalytic performance under UV light irradiation, such as PbTiO 3 , 7 BaTiO 3 , 8 Na 0.5 Bi 0.5 TiO 3 , 9 and Bi 3 TiNbO 9 , 10,11 among which, PbTiO 3 is regarded as one of the most promising photocatalysts because of its high built-in electric field (∼3.6 kV cm −1 ), adjustable micromorphology and band gap (∼2.8 eV). 7,12 By controlling surface defects 13 and spatially selective adsorption of redox mediators, 14 PbTiO 3 has been utilized in single particle and Z-scheme photocatalytic overall water splitting reactions.…”

“…The wide band gap ferroelectric photocatalysts explored exhibit excellent photocatalytic performance under UV light irradiation, such as PbTiO 3 , 7 BaTiO 3 , 8 Na 0.5 Bi 0.5 TiO 3 , 9 and Bi 3 TiNbO 9 , 10,11 among which, PbTiO 3 is regarded as one of the most promising photocatalysts because of its high built-in electric field (∼3.6 kV cm −1 ), adjustable micromorphology and band gap (∼2.8 eV). 7,12 By controlling surface defects 13 and spatially selective adsorption of redox mediators, 14 PbTiO 3 has been utilized in single particle and Z-scheme photocatalytic overall water splitting reactions. However, its theoretical solar energy conversion efficiency is severely limited by the lack of visible light absorption.…”