Large dipole moment induced wide-spectrum bismuth chromate for efficient photocatalytic performance

February 07, 2020

The conversion and utilization of solar energy for chemical fuel production and environmental remediation through artificial photocatalysis have been recognized to be an ideal route to address the critical energy and environmental concerns. The full utilization of solar light is a great challenge for achieving sufficient efficiency in practical applications, and narrowing the bandgap of a photocatalyst weakens the driving force for redox reactions, especially water oxidation and pollutant degradation, because these reactions involve a complicated multi-electron process. Therefore, the development wide-spectrum responsive and highly efficient photocatalysts for water oxidation and pollutant degradation is a critical issue to be addressed at present.

Bi-based oxometallate materials, such as BiVO4¬, Bi2WO6, Bi2MoO6, etc., have been widely studied as visible-light active photocatalysts and exhibit excellent photocatalytic performance in water oxidation and pollutant degradation, which is mainly benefiting from their sufficiently deep valence band position. In this work, a wide-spectrum responsive Bi8(CrO4)O11 nanorod photocatalyst was successfully constructed. Owing to the hybridization of Cr 3d with O 2p orbitals shifts conduction band minimum down, Bi8(CrO4)O11 allows its absorption up to the entire visible region (~678 nm) with a theoretical solar spectrum efficiency of 42.0%. And its VB of 1.95 eV (vs. NHE pH=7) is more positive than the oxidation potential of OH-/O2, which indicates that the photogenerated holes of Bi8(CrO4)O11 nanorod photocatalyst possess extremely strong oxidation capability.

As shown in Figure 1a, Bi8(CrO4)O11 exhibited exceedingly superior photocatalytic water oxidation performance, and its average O2 evolution rate reached 14.94 μmol h-1, about 11.5 and 4.0 times higher than that of Bi2WO6 nanosheets and commercial WO3 nanoparticles. Besides, it consequently achieved a considerable apparent quantum efficiency (AQE) 2.87% at 420 nm, even 0.65% at 650 nm (Figure 1b), higher than many reported wide-spectrum driven photocatalysts. Most noticeably, its excellent activity is also manifested in photocatalytic degradation of phenol. Its degradation reaction constant could reach 0.119 min-1, about 22.5 and 8.8 times higher than CdS nanowires and PDI supramolecular photocatalysts, respectively (Figure 1c). Even its degradation activity is not inferior to P25 TiO2 under simulated sunlight, about 2.9 times higher than the latter. Remarkably, Bi8(CrO4)O11 also presented extremely strong mineralization ability, which almost enables the simultaneous degradation and complete mineralization for phenol. The total organic carbon removal rates of phenol over Bi8(CrO4)O11 under visible light and simulated sunlight is 94.8% (degradation rate: 95.5%) and 97.3% (degradation rate: 98.1%) in 0.5 h, respectively, while that of CdS, PDI and P25 are significantly lower than their corresponding degradation rates. Even under 650 nm red light irradiation, Bi8(CrO4)O11 is still able to simultaneously degrade and completely mineralize phenol (Figure 1d), and few wide-spectrum driven photocatalysts can achieve that.

Besides, the dipole moments of Bi8(CrO4)O11 was calculated to 22.32 Debye (D), which results in a giant internal electric field (IEF). As shown in Figure 1e, compared to Bi14CrO24, Bi8(CrO4)O11 with a greater dipole showed a significantly higher IEF, charge separation efficiency and photocatalytic performance. Therefore, as illustrated in Scheme 1, the large crystal dipole of Bi8(CrO4)O11 induces a giant IEF, which accelerates the rapid separation of photogenerated electron-hole pairs and exponentially enhances its photocatalytic performance. Most importantly, based on the above mechanism, many more efficient photocatalysts can be designed successfully by regulating the crystal dipole.
-end-
This research was supported by the National Natural Science Foundation of China (grant numbers 21872077, 21437003, 21673126, 21761142017, and 21621003) and the Collaborative Innovation Center for Regional Environmental Quality.

See the article:

Xianjie Chen, Yuan Xu, Xinguo Ma, Yongfa Zhu

Large dipole moment induced efficient bismuth chromate photocatalysts for wide-spectrum driven water oxidation and complete mineralization of pollutants

Natl Sci Rev; doi: 10.1093/nsr/nwz198

https://doi.org/10.1093/nsr/nwz198

The National Science Review is the first comprehensive scholarly journal released in English in China that is aimed at linking the country's rapidly advancing community of scientists with the global frontiers of science and technology. The journal also aims to shine a worldwide spotlight on scientific research advances across China.

Science China Press

Related Water Articles from Brightsurf:

Transport of water to mars' upper atmosphere dominates planet's water loss to space
Instead of its scarce atmospheric water being confined in Mars' lower atmosphere, a new study finds evidence that water on Mars is directly transported to the upper atmosphere, where it is converted to atomic hydrogen that escapes to space.

Water striders learn from experience how to jump up safely from water surface
Water striders jump upwards from the water surface without breaking it.

'Pregnancy test for water' delivers fast, easy results on water quality
A new platform technology can assess water safety and quality with just a single drop and a few minutes.

Something in the water
Between 2015 and 2016, Brazil suffered from an epidemic outbreak of the Zika virus, whose infections occurred throughout the country states.

Researchers create new tools to monitor water quality, measure water insecurity
A wife-husband team will present both high-tech and low-tech solutions for improving water security at this year's American Association for the Advancement of Science (AAAS) annual meeting in Seattle on Sunday, Feb.

The shape of water: What water molecules look like on the surface of materials
Water is a familiar substance that is present virtually everywhere.

Water, water everywhere -- and it's weirder than you think
Researchers at The University of Tokyo show that liquid water has 2 distinct molecular arrangements: tetrahedral and non-tetrahedral.

What's in your water?
Mixing drinking water with chlorine, the United States' most common method of disinfecting drinking water, creates previously unidentified toxic byproducts, says Carsten Prasse from Johns Hopkins University and his collaborators from the University of California, Berkeley and Switzerland.

How we transport water in our bodies inspires new water filtration method
A multidisciplinary group of engineers and scientists has discovered a new method for water filtration that could have implications for a variety of technologies, such as desalination plants, breathable and protective fabrics, and carbon capture in gas separations.

Source water key to bacterial water safety in remote Northern Australia
In the wet-dry topics of Australia, drinking water in remote communities is often sourced from groundwater bores.

Read More: Water News and Water Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.