Efficient Photocatalytic Oxygen Production over Nitrogen‐Doped Sr₄Nb₂O₉ under Visible‐Light Irradiation

Abstract

Photocatalytic water splitting is an appealing process for solar energy conversions yet it is often limited by the slow oxidation of water to oxygen half‐reaction. Here we performed an investigation on N‐doped Sr4Nb2O9 as a water oxidation photocatalyst. Our results show that N doping is an effective approach to improve the visible‐light response of Sr4Nb2O9. Efficient photocatalytic oxygen production was observed after N doping, and the highest production rate of ∼27 μmol h−1 under visible‐light irradiation corresponds to an apparent quantum efficiency of ∼0.31 %. Clear anodic photocurrent can be generated under visible‐light illumination, and the flat‐band potential was determined to be ∼−1.25 V vs. Ag/AgCl at pH 7. Theoretical calculations reveal that N doping introduces additional valence bands and is responsible for the visible‐light response. Variations in light absorption and photo‐oxidation performance can be controlled by modifying these valence band positions using different nitridation temperatures.

Ultrathin Lanthanum Tantalate Perovskite Nanosheets Modified by Nitrogen Doping for Efficient Photocatalytic Water Splitting

“…The absorption edge of RbLaTa 2 O 7 is red-shifted by almost 300 nm after nitrogen doping which effectively turns its color from white to orange (Figure a,b). XPS spectra confirm the existence of N 1s signal at bind energy around 395 eV in sample RbLaTa 2 O 6.77 N 0.15 , corresponding to lattice N 3– species. , The Ta 4p 3/2 state, however, remains almost intact before and after nitrogen doping, suggesting that the color change does not stem from reduction of Ta 5+ such as Ta 4+ species. ,, The intense visible light absorption as well as band gap reduction for RbLaTa 2 O 6.77 N 0.15 compared with pristine one origin primarily from the uplifting of the VBM, as can be seen from the XPS valence band scan (Figure d). DFT calculation suggests that VBM for RbLaTa 2 O 6.77 N 0.15 has substantial N 2p characters and band gap reduction is due to the hybridization between N 2p orbitals with O 2p orbitals which uplifts the VBM (Figure S3).…”

“…XPS spectra confirm the existence of N 1s signal at bind energy around 395 eV in sample RbLaTa 2 O 6.77 N 0.15 , corresponding to lattice N 3− species. 36,39 The Ta 4p 3/2 state, however, remains almost intact before and after nitrogen doping, suggesting that the color change does not stem from reduction of Ta 5+ such as Ta 4+ species. 28,29,40 The intense visible light absorption as well as band gap reduction for RbLaTa 2 O 6.77 N 0.15 compared with pristine one origin primarily from the uplifting of the VBM, as can be seen from the XPS valence band scan (Figure 2d).…”

Role of Oxygen Defects on the Photocatalytic Properties of Mg‐Doped Mesoporous Ta3N5

“…Photoelectrodes from the as‐prepared samples were prepared by an electrophoretic deposition method: two pieces of fluorine doped tin oxide (FTO) glass (30×10 mm) were immersed in 50 mL acetone solution containing 50 mg sample powders and 10 mg iodine. The two pieces of glass were kept in parallel with a 10 mm separation and the conductive sides facing inward.…”

Quinary wurtzite Zn-Ga-Ge-N-O solid solutions and their photocatalytic properties under visible light irradiation

“…Microstructure analysis reveals a strong correlation between high crystallinity and high catalytic activity. However, particles of (Ga 1-x Zn x )(N 1-x O x ) solid solution under SEM conditions all appear to be irregular, even under optimized synthetic procedures 9 . This was also confirmed in our study that sample prepared by nitridizing Ga 2 O 3 and ZnO mixtures contains featureless particles, ranging from hundred nanometers to micron in diameter ( Fig.…”

“…Ideally, such a process includes a simple uphill reaction that water molecules are split into hydrogen and oxygen at the surface of a semiconductor, driven solely by incoming photons. Materials suitable for this reaction have to be light sensitive and catalytically active simultaneously, which by far is subject to only a few compounds or systems 1 2 3 4 5 6 7 8 9 10 . In particular, complete water splitting using visible light photons (λ ≥ 400 nm) is only reported in some metal oxides/oxynitrides containing elements with d 10 electronic configurations 11 12 13 and an organic semiconductor g-C 3 N 4 with carbon nanodots 14 .…”