The contrasting effect of the Ta/Nb ratio in (111)-layered B-site deficient hexagonal perovskite Ba₅Nb_4−xTa_xO₁₅ crystals on visible-light-induced photocatalytic water oxidation activity of their oxynitride derivatives

Abstract

The effect of the Ta/Nb ratio in the (111) the Ta content up to 50 mol% but decreased at 75 and 100 mol% presumably due to the reduced specific surface area and high density of structural defects, such as grain boundaries acting as recombination centers, originated from high-temperature nitridation for prolonged periods. Transient absorption spectroscopy provided evidence for the effect of the Ta/Nb ratio on the behavior and energy states of photogenerated charge carriers, indicating a direct correlation with photocatalytic water oxidation activity of BaNb 1−x Ta x O 2 N.

Effective masses, electronic and optical properties of (111)-layered B-site deficient hexagonal perovskite Ba5M4O15(M = Ta, Nb): a DFT study using HSE06

“…23 All calculations in this paper were carried out using the Cambridge Serial Total Energy Package (CASTEP), 24 which uses a plane wave expansion technology in reciprocal space. 23 All calculations in this paper were carried out using the Cambridge Serial Total Energy Package (CASTEP), 24 which uses a plane wave expansion technology in reciprocal space.…”

“…Thus, they are regarded as cation-decient perovskite. 23 In this work, we have comparatively studied the equilibrium lattice parameters, electronic structures and optical properties of (111)-layered B-site decient hexagonal perovskite Ba 5 M 4 O 15 (M ¼ Ta, Nb) by the rst-principles computations on the basis of density functional theory using the norm-conserving-type pseudo-potential technique and screened nonlocal exchange-correlation functional HSE06 as dened by Heyd, Scuseria, and Ernzerhof. According to the electroneutrality requirement, one of the octahedral holes is empty, resulting in the loss of face sharing on the MO 6 sublattice and strong anharmonicity of these compounds.…”

Perovskite Sr1−x Ba x W1−y Ta y (O,N)3: synthesis by thermal ammonolysis and photocatalytic oxygen evolution under visible light

“…On the other hand, introducing the tungsten species having 5d 1 electronic configuration into the B-site of BaTaO 2 N showed an exceedingly effective impact on enhancing the photocatalytic water oxidation activity [15]. Furthermore, the CoO x -loaded BaNb 1-x Ta x O 2 N porous structures (x = 0.50) exhibited higher photocatalytic O 2 evolution rate (127.24 lmol in the first 2 h) than the CoO x -loaded pure BaNbO 2 N porous structures (20.92 lmol in the first 2 h) owing to the high specific surface area and low density of structural defects [16]. As mentioned above, the photocatalytic activity of AB(O,N) 3 can be significantly enhanced by the exquisite combination of the substitutional elements and parent materials, which still has many untouched possibilities to explore.…”

Synthesis and visible-light-induced sacrificial photocatalytic water oxidation of quinary oxynitride BaNb0.5Ta0.5O2N crystals

“…After the partial nitridation and acidification, the outline of the oxide precursor (Ba 5 Nb 2 Ta 2 O 15 ) was retained and the small pores (ca. 30 nm) appear on the surface of the asgrown BaNb 0.5 Ta 0.5 O 2 N crystals due possibly to the phase transitions from hexagonal oxide to cubic oxynitride, dissolution of BaO, and lattice shrinkage because of the partial replacement of O 2 − with N 3 − in the oxide precursor [14,20,21] . The EDS elemental mapping images of the as-grown BaNb 0.5 Ta 0.5 O 2 N crystals clearly exhibit the even distribution of Ba (purple), Nb (cyan), Ta (blue), O (yellow), and N (green) elements through the crystals, indicating that the tantalum and nitrogen were partially incorporated into the BaNbO 2 N lattice (see Fig.…”

“…Recently, our group has attempted to improve the sacrificial photocatalytic water oxidation activity of BaNbO 2 N by partially substituting Ta 5 + into Nb 5 + : BaNb 1 −x Ta x O 2 N crystals were fabricated by partial nitridation of KCl flux grown Ba 5 (Nb 1 −x Ta x ) 4 O 15 crystals. For the optimal Ta substitution level of 50 at%, BaNb 0.5 Ta 0.5 O 2 N exhibited six times higher oxygen evolution rate compared to pure BaNbO 2 N due to the high specific surface area and low density of structural defects such as grain boundaries [14] .…”