Perovskite BaTaO₂N: From Materials Synthesis to Solar Water Splitting

Abstract

Barium tantalum oxynitride (BaTaO2N), as a member of an emerging class of perovskite oxynitrides, is regarded as a promising inorganic material for solar water splitting because of its small band gap, visible light absorption, and suitable band edge potentials for overall water splitting in the absence of an external bias. However, BaTaO2N still exhibits poor water‐splitting performance that is susceptible to its synthetic history, surface states, recombination process, and instability. This review provides a comprehensive summary of previous progress, current advances, existing challenges, and future perspectives of BaTaO2N for solar water splitting. A particular emphasis is given to highlighting the principles of photoelectrochemical (PEC) water splitting, classic and emerging photocatalysts for oxygen evolution reactions, and the crystal and electronic structures, dielectric, ferroelectric, and piezoelectric properties, synthesis routes, and thin‐film fabrication of BaTaO2N. Various strategies to achieve enhanced water‐splitting performance of BaTaO2N, such as reducing the surface and bulk defect density, engineering the crystal facets, tailoring the particle morphology, size, and porosity, cation doping, creating the solid solutions, forming the heterostructures and heterojunctions, designing the photoelectrochemical cells, and loading suitable cocatalysts are discussed. Also, the avenues for further investigation and the prospects of using BaTaO2N in solar water splitting are presented.

Nanostructured (oxy)nitrides controllably synthesized by flux-assisted nitridation for promoted photocatalytic water splitting

“…In this group, various (oxy)nitrides with an absorption edge range of 515-770 nm have been developed, such as CaTaO 2 N (515 nm), TaON (520 nm), SrTaO 2 N (570 nm), Ta 3 N 5 (590 nm), CaNbO 2 N (600 nm), LaTiO 2 N (620 nm), LaTaON 2 (640 nm), BaTaO 2 N (650 nm), SrNbO 2 N (700 nm), BaNbO 2 N (740 nm), and LaNbO 2 N (770 nm). 26,[69][70][71][72][73][74][75][76][77][78] It is worth noting that longer wavelengths of the solar spectrum can be utilized over d 0 -based (oxy) nitrides than d 10 -based (oxy)nitrides. For example, BaTaO 2 N has an absorption edge of 650 nm, which can be modied for one-step photoexcited OWS.…”

“…[16][17][18][19][20][21][22][23][24][25] Among them, the (oxy)nitrides have drawn more attention due to the features of excellent electronic and optical properties and outstanding energy band structures. 11,26 Currently, how to prepare (oxy)nitrides with enhanced charge utilization is the mainstream in this eld. [27][28][29] Generally, (oxy)nitrides are synthesized via a high-temperature nitridation process using ammonia and metal oxides as a nitrogen source and precursors, respectively.…”

“…In addition, the nitrided particles tend to aggregate together with poor control in morphology, particle size, and purity. 26,30,31 To alleviate those issues, the ux-assisted nitridation method has been developed recently for the preparation of the promoted (oxy)nitrides. 32,33 In this route, the ux was introduced as the reaction solvent during the nitridation, which could accelerate the mass transfer, promote the nitridation kinetics, and improve the dispersity of the formed (oxy)nitrides.…”

“…16–25 Among them, the (oxy)nitrides have drawn more attention due to the features of excellent electronic and optical properties and outstanding energy band structures. 11,26 Currently, how to prepare (oxy)nitrides with enhanced charge utilization is the mainstream in this field. 27–29…”

Untangling the Effect of Carbonaceous Materials on the Photoelectrochemical Performance of BaTaO2N

“…BaTaO 2 N is a promising visible-light-active photocatalyst for water oxidation due to its capability to absorb visible light up to 660 nm, appropriate band-edge potential straddling the water oxidation reaction potential, good stability in concentrated alkaline solution, and nontoxicity. , Under AM 1.5G simulated sunlight based on an incident photon-to-current conversion efficiency (IPCE) of 100% at <660 nm, the photocurrent density and solar-to-hydrogen (STH) conversion efficiency are assumed to reach approximately 18 mA cm –2 and 24%, respectively. , To achieve higher efficiency in solar water splitting over BaTaO 2 N, various strategies, such as band-gap engineering via mono- and dual-substitution , and solid solutions, , controlling the defect density, − fabricating thin films, , tailoring the exposed surface, morphology, and size, − etc., were applied. Photocurrent densities of ∼0.03, >1.2, 2.05, 4.2, ∼4.5, and 6.5 mA cm –2 at 1.2 V vs the reversible hydrogen electrode were progressively achieved for BaTaO 2 N, while incident photon-to-current efficiencies of 1% at 500 nm, >4% at 400 nm, 13% at 420 nm, ∼30% at 400 nm, 34–35% at 380–540 nm, and ≈43% IPCE at 540 nm at 1.2 V vs RHE steadily increased.…”