Construction of Spatial Charge Separation Facets on BaTaO₂N Crystals by Flux Growth Approach for Visible-Light-Driven H₂ Production

Abstract

Low charge separation efficiencies are regarded as obstacles that limit the improvement in the photocatalytic performance of BaTaO2N. In this study, we demonstrated that the anisotropic facets ({100} and {110} facets) of BaTaO2N for efficient spatial charge separation were successfully constructed using the one-pot flux-assisted nitridation approach. As a result, the photocatalytic activity for H2 production on BaTaO2N with coexposed {100} and {110} facets was nearly 10-fold over that of BaTaO2N with only {100} facets and that of the conventional irregularly shaped sample. This finding provides an innovative approach to the development of efficient (oxy)­nitride photocatalysts for solar energy conversion.

Sequential cocatalyst decoration on BaTaO2N towards highly-active Z-scheme water splitting

“…Preparation of Pt-modified BaTaO 2 N. The preparation of BaTaO 2 N, loading of Pt nanoparticles on BaTaO 2 N, and the photocatalytic H 2 production and Z-scheme water splitting, are described in detail in the subsections of "Methods". Briefly, BaTaO 2 N was synthesized by one-pot nitridation of a BaCO 3 and Ta 2 O 5 mixture with the assistance of molten RbCl or other alkali chlorides (NaCl, KCl, or CsCl) fluxes at 1223 K for 8 h under a flow of gaseous NH 3 (200 mL min −1 ) 24,34 . BaTaO 2 N prepared by using RbCl, NaCl, KCl, and CsCl fluxes are denoted as BaTaO 2 N (RbCl), BaTaO 2 N (NaCl), BaTaO 2 N (KCl), and BaTaO 2 N (CsCl), respectively.…”

“…The materials properties of BaTaO 2 N (RbCl) were examined because BaTaO 2 N (RbCl) exhibited greater H 2 evolution activity than BaTaO 2 N synthesized by using the other alkali chloride fluxes when being decorated with Pt by photodeposition 24,34 . The X-ray diffraction pattern ( Supplementary Fig.…”

“…13b), and XPS analysis ( Supplementary Fig. 11), RbCl flux-assisted nitridation process enabled the formation of well-crystallized BaTaO 2 N with minimized defects (reduced Ta 5+ species and anion vacancies) 24,34 . Moreover, the amount of alkali metal ions incorporated in the BaTaO 2 N materials during the flux-assisted nitridation became less with the increase of their ionic radii (Supplementary Table 5 and Supplementary Fig.…”

“…Perovskite-type BaTaO 2 N with a bandgap of around 1.8 eV is a photocatalyst material that has been intensively studied for Z-scheme water splitting 15,16,22,23 , as well as H 2 or O 2 evolution half-reactions using sacrificial reagents 15,[24][25][26][27] (see Supplementary Table 2). The BaTaO 2 N photocatalyst intrinsically exhibits a weak driving force for surface redox reactions 14 , and loading of cocatalysts such as nanoparticulate Pt is essential to promote the extraction of photogenerated charge carriers from BaTaO 2 N for efficient H 2 evolution 22,23,[28][29][30][31][32][33] .…”

Defect Engineering for Photocatalysis: From Ternary to Perovskite Oxynitrides

“…The most common surface treatment strategy in this respect is loading the photocatalyst with particulate co‐catalysts such as CoO x , cobalt phosphate and IrO x . Beyond co‐catalyst loading however, other surface/interface treatments for perovskite oxynitrides that have been reported in the literature include post‐synthetic annealing in Ar or N 2 /H 2 , construction of heterojunctions, and most recently the engineering of different surface facets on a particulate photocatalysts to promote charge segregation . Engineering of perovskite oxynitride surfaces however is understood far less, compared to perovskite oxides.…”