Growth of BaTaO ₂ N–BaNa _0.25 Ta _0.75 O ₃ Solid Solution Photocatalyst for Visible Light-Driven Z-Scheme Overall Water Splitting

Abstract

BaTaO 2 N with intense visible light absorption has been demonstrated as a promising photocatalyst for Z-scheme overall water splitting, whereas the photocatalytic activity of BaTaO 2 N is still restricted by strong charge recombination at structural defects. Here, we present the direct growth of BaTaO 2 N–BaNa 0.25 Ta 0.75 O 3 solid solution from a lattice-matched BaNa 0.25 Ta 0.75 O 3 precursor through volatilization of Na species during a nitridation process. This method promotes the direct phase transformation from BaNa 0.25 Ta 0.75 O 3 to BaTaO 2 N to inhibit the formation of defect states. As a result, the as-obtained BaTaO 2 N–BaNa 0.25 Ta 0.75 O 3 solid solution shows greatly enhanced activity compared to the conventional BaTaO 2 N, regardless of photocatalytic H 2 evolution in the presence of methanol or Z-scheme overall water splitting. This study provides a facile method to construct (oxy)nitride-based solid solution photocatalysts with low defect density for efficient solar hydrogen production from water splitting.

Electrochemical Properties of BaTaO2N Photocatalyst with Visible‐Light‐Driven Water Splitting Capability

“…The results of peak fitting for Ta 4 f led us to determine the presence of Ta(O), Ta(N), and Ta 3+ with a spin‐orbital separation of 1.9 eV between Ta 4f 7/2 and Ta 4f 5/2 (Figure S5 and Table S2). The BE of Ta(O) was higher than that of Ta(N) due to the higher electronegativity of the O atom compared to the N atom [14b,21] …”

Perovskite BaTaO2N: From Materials Synthesis to Solar Water Splitting

“…The BaTaO 2 N–BaNa 0.25 Ta 0.75 O 3 solid solution was synthesized by the ammonolysis of BaNa 0.25 Ta 0.75 O 3 oxide precursor having a lattice‐matched crystal structure with BaTaO 2 N and containing volatile Na. [ 187 ] During high‐temperature ammonolysis, the lattice matching decreased the thermodynamic barrier of atomic diffusion rearrangement, and the sublimation of Na facilitated the direct phase transition of BaNa 0.25 Ta 0.75 O 3 to BaTaO 2 N. These processes significantly inhibited the formation of defects. Therefore, the BaTaO 2 N‐BaNa 0.25 Ta 0.75 O 3 solid solution exhibited higher photocatalytic activity (54.62 µmol h −1 ) for H 2 evolution than pristine BaTaO 2 N (3.56 µmol h −1 ; Figure a–c).…”

“…Since Pt‐modified BaTaO 2 N–BaNa 0.25 Ta 0.75 O 3 solid solution exhibited an enhanced photocatalytic activity for H 2 evolution, Luo et al. [ 187 ] further studied the Z‐scheme overall water splitting by involving the BaTaO 2 N–BaNa 0.25 Ta 0.75 O 3 solid solution as the H 2 ‐evolving photocatalyst, surface‐treated WO 3 as the O 2 ‐evolving photocatalyst, and IO 3 − /I − as a redox mediator under visible light irradiation. The system prepared with the BaTaO 2 N–BaNa 0.25 Ta 0.75 O 3 solid solution exhibited the highest photocatalytic activity with 14.46 µmol h −1 H 2 and 6.68 µmol h −1 O 2 evolution rates (Figure 19a).…”

“…No solid solutions between CaTaO 2 N and BaTaO 2 N Reproduced with permission. [187] Copyright 2022, American Association for the Advancement of Science. d) TEM and HRTEM images of Ba(0.3)-Ta 3 N 5 sample, e) Mott-Schottky plots and schematic representation of band structures of Ta 3 N 5 and BaTaO 2 N, and f) multiple cycles of Z-scheme overall water splitting with 0.5 wt% Pt/Ba(0.3)-Ta 3 N 5 and 0.45 wt% PtO x /WO 3 .…”

“…The BaTaO 2 N shell on Ta 3 N 5 nanorods improved visible light harvesting, leading to the efficient generation and extraction of charge carriers and a stable evolution of stoichiometric O 2 (36.2 μmol h −1 cm −2 ) and H 2 (72.4 μmol h −1 cm −2 ) with Faradaic efficiencies near 96% (Figure 20d). Since Pt-modified BaTaO 2 N-BaNa 0.25 Ta 0.75 O 3 solid solution exhibited an enhanced photocatalytic activity for H 2 evolution, Luo et al [187] further studied the Z-scheme overall water splitting by involving the BaTaO 2 N-BaNa 0.25 Ta 0.75 O 3 solid solution as the H 2 -evolving photocatalyst, surface-treated WO 3 as the O 2 -evolving photocatalyst, and IO 3 − /I − as a redox mediator under visible light irradiation. The system prepared with the BaTaO 2 N-BaNa 0.25 Ta 0.75 O 3 solid solution exhibited the highest photocatalytic activity with 14.46 μmol h −1 H 2 and 6.68 μmol h −1 O 2 evolution rates (Figure 19a).…”