Charge Carrier Dynamics in Sr-Doped NaTaO₃ Photocatalysts Revealed by Deep Ultraviolet Single-Particle Microspectroscopy

Abstract

Among various metal oxides, sodium tantalate (NaTaO3) is one of the best semiconductors for achieving efficient photocatalytic water splitting. However, the primary mechanism responsible for increasing the reaction rate up to an order of magnitude by specific metal doping and surface modification with co-catalysts has not been elucidated yet. In order to clarify the underlying mechanism, we explored the structure-dependent photoluminescence (PL) of pristine and Sr-doped NaTaO3 crystals at the (near) single-particle level using a time-resolved deep ultraviolet fluorescence microscope. Combined with transmission electron microscope (TEM) techniques, the PL characteristics of individual particles were directly linked to the dopant concentrations in each particle, allowing us to unravel the complex effects of Sr-doping on the charge carrier dynamics. Furthermore, we investigated the photocatalytic reduction reaction for a single Sr-doped NaTaO3 particle to gain critical information related to dopantdriven electron migration, which is a key process for efficient photocatalysis.

Advances in Z‐scheme semiconductor photocatalysts for the photoelectrochemical applications: A review

“…Furthermore, it is possible to combine properties, such as ferroelectricity or piezoelectricity, with the photocatalytic effect to improve photocatalytic activity. The perovskite photocatalysts can be classified into the following categories: titanates, SrTiO 3 112–118 and BaTiO 3 119–123 ; tantalates, LiTaO 3 , 124 NaTaO 3 125–132 and KTaO 3 133–137 ; niobates, LiNbO 3 , 138,139 NaNbO 3 140–147 and KNbO 3 148–153 ; vanadates, AgVO 3 154–162 ; and ferrites, LaFeO 3 , 164–169 BiFeO 3 170–176 and GaFeO 3 177 . These compounds show great potential for application in visible light‐driven photoreactions.…”

Band Gap Narrowing of Bi-Doped NaTaO3 for Photocatalytic Hydrogen Evolution under Simulated Sunlight: A Pseudocubic Phase Induced by Doping

“…For this reason, several doping and heterojunction strategies have been proposed as an attempt to overcome this limitation by tuning the electronic band structure of the material. 4,20 Some of the most successful approaches for enhancing the photocatalytic activity of NaTaO 3 consist of La 3+ and Sr 2+ doping, 21,22 which improve charge transfer in the material 23,24 and induce surface reconstruction by creating steplike nanostructures that notably increase the surface area for water splitting reactions. 25 Despite these effects, La and Sr doping are only beneficial to the production of hydrogen under UV light, as these elements have negligible influence on the band gap.…”

Bi-doped NaTaO3 photocatalysts for hydrogen production under simulated sunlight: band gap narrowing and structural transitions

“…34 Some doping approaches have achieved significant progress in enhancing the photocatalytic activity of NaTaO3. Some of the most successful strategies consist of La 3+ 55 and Sr 2+ 47 doping, which are shown to enhance charge transfer [56][57] and promote surface reconstruction with the formation of step-like nano-structures that multiply the available area for water splitting reactions. 58 Regardless of these favourable effects, Sr and La doping are only beneficial to hydrogen evolution under UV light, since these dopants show no influence on the band gap.…”