Dependence of Photoexcited Electron Behavior on Octahedral Distortion in Barium-Doped NaTaO₃ Photocatalysts

Abstract

This study aims to investigate the behavior of photoexcited electrons in intentionally distorted Ba-doped NaTaO3 photocatalysts with time-resolved microwave conductivity and steady-state IR absorption induced by UV light. As probed by X-ray absorption fine structure and Raman spectroscopies, doping NaTaO3 with Ba2+ produces structural nonperiodicity and distorts the octahedral sublattice, proposedly resulting in the formation of electron traps. A higher density of shallow electron traps is suggested to be responsible for the longer electron lifetime and larger electron population, because shallowly trapped electrons are less likely to recombine with holes. The half-lifetime of photoexcited electrons is considerably long, even longer than 0.8 ms in the Ba-doped NaTaO3 sample with moderate distortion. The population of photoexcited electrons under Hg–Xe lamp irradiation increases by 32 times in this sample compared to that in undoped NaTaO3, generating H2/O2 mixtures with the rates of 385 μmol h–1 (H2) and 180 μmol h–1 (O2) when irradiated with a Hg lamp in the absence of cocatalyst and sacrificial compound. Moderate distortion seems favorable to produce shallow electron traps in comparison to large and small distortions, leading to the highest water splitting rate. The orders of photocatalysts based on their electron lifetime, electron population, and water splitting rate are identical, indicating that the photoexcited electrons worked in the water splitting reactions.

Unleashing the Potential of Coupled Substituted 3D Niobate Perovskite Oxides in Cocatalyst-free Photocatalytic Hydrogen Evolution

“…Recently, the effect of distortion in a Ba-doped perovskite tantalate has been claimed to create shallow electron traps especially for compounds with moderate distortions in comparison to smaller or higher distortions . The compounds with shallow traps showed higher photocatalytic activity and higher PHE performance.…”

“…Recently, the effect of distortion in a Ba-doped perovskite tantalate has been claimed to create shallow electron traps especially for compounds with moderate distortions in comparison to smaller or higher distortions. 69 The compounds with shallow traps showed higher photocatalytic activity and higher PHE performance. An inspection of the octahedral distortion parameter (Table S5) calculated from the bond distances of refined structures indicated moderate octahedral distortion for the Cr compound, while that of the Co compound is the highest and Mn and Fe share the lowest distortion parameters.…”

Probing Charge Carrier Behavior in Engineered Photocatalysts with Time-Resolved Visible to Mid-IR Absorption Spectroscopy

“…An irreversible phase transition of anatase TiO 2 to rutile polymorph that affected the transient signals were also reported by the same group. 197 Another challenge while rationalizing charge carrier behavior with TRVIR is associated with the nature of the experiment, which is different from that in the typical steady-state photocatalytic reactions, such as overall water splitting, 198 water reduction, 199 or organic compound oxidation. 200 Photocatalytic experiments adopt much less intense light irradiation than pump−probe experiments and are typically performed in an aqueous suspension (a slurry system) at ambient pressure.…”

Critical Role of the NiO–Ni(OH)2 Species Loaded Onto TiO2 Photocatalyst in the Enhancement of H2 Evolution Activity

“…At present, the efficiency of artificial photosynthesis exceeds that of natural photosynthesis. 1 It converts solar energy to chemical energy by splitting H 2 O into H 2 and O 2 , [2][3][4][5][6] or reacting CO 2 and H 2 O to sugars and high-energy chemicals. 7 In artificial photosynthesis research with particulatecatalyst, TiO 2 is often regarded as the benchmark.…”