Improving the Surface Oxygen Vacancy Concentration of Bi₂O₄ through the Pretreatment of the NaBiO₃·2H₂O Precursor as a High-Performance Visible Light Photocatalyst

Abstract

The oxygen-deficient bismuth oxide, Bi 2 O 4 , synthesized by a typical hydrothermal method using commercial NaBiO 3 • 2H 2 O as a raw material only has a relatively low concentration of surface oxygen vacancies (OVs). How to improve the visible light photocatalytic performance of Bi 2 O 4 via tuning its surface OV concentration is still a huge challenge. In this study, improving the surface OVs of Bi 2 O 4 was successfully realized through the pretreatment of commercial NaBiO 3 •2H 2 O, including thermal treatment in air and hydrothermal treatment in 10 M NaOH solution, forming NaBiO 3 •xH 2 O intermediate products first, and then hydrothermal preparation of Bi 2 O 4 target products using NaBiO 3 •xH 2 O instead of commercial NaBiO 3 •2H 2 O as the precursor. The enhanced surface OV content not only narrows the band gap of Bi 2 O 4 and thus extends its optical response range but also captures more photoexcited electrons and thus increases the charge carriers' separation efficiency and prolongs the charge carriers' lifetime of Bi 2 O 4 . Among the above-mentioned two pretreatment methods, the effects of the hydrothermal pretreatment are superior to those of the thermal treatment, involving the increase of surface OVs, the optical harvesting capacity, and the charge carriers' separation efficiency. Accordingly, Bi 2 O 4 prepared by the hydrothermal pretreatment route exhibits the optimal visible light catalytic performance toward the removal of methyl orange (MO) and phenol due to its most abundant surface OV concentration, which is 2.59 times and 4.26 times higher than that of Bi 2 O 4 synthesized directly by the commercial NaBiO 3 •2H 2 O route, respectively. Holes (h + ) and superoxide radicals ( • O 2 − ) are identified as the main active species, while singlet oxygen ( 1 O 2 ) and hydroxyl radicals ( • OH) are verified as the second and third important active species for organic pollutant removal, respectively. This work has developed a novel strategy to promote the catalytic performance of single Bi 2 O 4 induced by the enhanced surface OV concentration through the pretreatment of the precursor, commercial NaBiO 3 • 2H 2 O.

Improved visible light triggered photocatalytic activities of BiOCl photocatalysts via a synergistic effect of doping and heterojunction engineering

“…5(b), one knows that both O 2− 1s (530.1 eV) and oxygen vacancy (533.2 eV) exist in the studied photocatalysts. 27 As confirmed in previous literature reports, 46,47 one knows that the oxygen vacancy presented in the semiconductor can improve its light harvest capacity in the visible region, resulting in robust photocatalytic activity. 47 Besides, the HR Cl − XPS spectrum is also able to be split into two peaks at 198.1 and 199.7 eV arising from Cl − 2p 3/2 and Cl − 2p 1/2 , respectively, as demonstrated in Fig.…”

A Comprehensive Review on Non‐Trivalent Bismuth‐Based Materials: Structure, Synthesis, and Strategies for Improving Photocatalytic Performance

“…[ 55 ] Another work synthesized Bi 2 O 4 with different contents of surface OVs through hydrothermally treating NaBiO 3 · x H 2 O, which was in advance obtained from NaBiO 3 ·2H 2 O by heating in air atmosphere or under hydrothermal condition. [ 56 ] In summary, different from Bi 2 O 4 , the strategy of microstructure‐controlled synthesis of oxygen‐deficient BiO 4− x is still challenging.…”

Bi2O2CO3 Nanosheet Composites with Bi-Based Metal–Organic Frameworks for Photocatalytic H2O2 Production

“…Hydrogen peroxide (H 2 O 2 ), a chemically significant and environmentally friendly compound, has found widespread application in the realms of fuel cells, chemical synthesis, water purification, and pulp bleaching. − At present, H 2 O 2 is mainly produced by oxidizing anthraquinone in the industrial field. − However, producing hydrogen peroxide by the oxidation of anthraquinone involves many oxidation reactions in organic solvents. These oxidation reactions usually not only require a large amount of energy consumption but also produce a lot of waste. , Furthermore, direct synthesis of H 2 O 2 by mixing H 2 and O 2 raises the explosion risk. , In contrast, the conversion of O 2 and H 2 O into H 2 O 2 by photocatalysts provides a promising approach in an environmentally friendly and safe way.…”