Endotaxial Growth of [100]‐Oriented TaON Films on LiTaO₃ Single Crystals for Enhanced Photoelectrochemical Water Splitting

Abstract

To enhance the photoelectrochemical (PEC) water splitting performance of TaON photoanodes, we grow [100]‐oriented TaON films by nitridating the (012) surface of single crystal LiTaO3 under NH3/CCl4 mixed gas. The endotaxial growth of [100]‐oriented TaON from the (012) surface of LiTaO3 produces TaON nanoporous films that can be completely exfoliated from the LiTaO3 substrate. The exfoliated film consists of interconnected worm‐like TaON nanoparticles aligned along the [100] direction perpendicular to the film surface across the film thickness. This oriented TaON porous nanostructure facilitates the transfer of photogenerated electrons across the film, hence enhancing the separation of photogenerated electron–hole pairs on the film surface. As a result, the TaON photoanode fabricated by the annealed oriented TaON films exhibits excellent PEC performances with a photocurrent of 5.32 mA cm−2 at 1.23 V versus RHE under AM 1.5 G simulated solar irradiation. This value is one of the highest photocurrents among the TaON photoanodes reported so far. Our work provides a new method to fabricate highly oriented crystalline films through an endotaxial growth process from single crystalline substrates. This method can be used to fabricate highly efficient photoelectrodes for PEC water splitting, and is expected to be useful in many other fields.

Flux‐Assisted Synthesis of Prism‐like Octahedral Ta3N5 Single‐Crystals with Controllable Facets for Promoted Photocatalytic H2 Evolution

“…It can be divided into two peaks located at ≈531.4 and 530.0 eV, which are ascribed to the chemisorbed O species and surface lattice oxygen species, respectively. [ 19 ] In addition, from Figure S3,Supporting Information, we can see that a small number of molten salt residues like Cl - were existed on the surface of Ta 3 N 5 sample, which were similarly detected in other reports involving flux growth [8a,20] . To summary, all the evidences that are earlier verified shows Ta 3 N 5 crystals grown by flux‐assisted nitridation exhibiting similar structure properties to the conventional Ta 3 N 5 nanoparticles.…”

Enhancing the Photoelectrochemical Water Oxidation Reaction of BiVO4 Photoanode by Employing Carbon Spheres as Electron Reservoirs

“…Photoelectrochemical (PEC) water splitting has attracted much attention in recent years owing to its capability of generating hydrogen and oxygen by utilizing solar energy with high theoretical solar-to-hydrogen (STH) conversion efficiency at a low cost. − Moreover, the hydrogen and oxygen evolution reactions take place at the photocathode and photoanode, respectively, which can be easily collected at two separated electrodes for large-scale production. − Therefore, the PEC water splitting is regarded as one of the most promising ways to produce hydrogen and hence help solve the energy crisis in the future. − However, the rate of the photoanode reaction is 4 orders of magnitude lower than that of the two-electron water reduction reaction at the photocathode. Therefore, the slow water oxidation reaction at the photoanode is the rate-determining step that governs the reaction rate of the PEC water splitting. − …”

Charge Carrier Transport Mechanism in Ta2O5, TaON, and Ta3N5 Studied by Applying Polaron Hopping and Bandlike Models

“…These materials are obtained by nitrogen doping or nitridation of its counterpart oxides. The β-TaON could oxide the water to O 2 and reduce H + to H 2 , [1,2] and it is widely used as photoanode for water oxidation with cocatalysts, [3][4][5] and also used as a H 2 -evolving photocatalyst (HEP) in the photocatalytic Z-scheme overall water splitting. [6] β-Ta 3 N 5 is considered to be the most important polymorphs in the practice, and it is used as particles in PC or photoanodes in PEC water splitting under visible light irradiation.…”