AsianScientist (Feb. 7, 2019) – Scientists in China have combined black phosphorus nanolayers with bismuth tungstate to produce an efficient catalyst that breaks down nitrogen monoxide (NO) and produces hydrogen. Their findings are published in the journal Angewandte Chemie.
Just as plants photosynthesize, certain semiconductors can absorb light energy and use it to drive chemical reactions. For example, bismuth tungstate (Bi2WO6) could be used for the photocatalytic degradation of NO and the production of hydrogen, but its conversion efficiency is extremely low.
One approach to improving the performance of bismuth tungstate is to bind two-dimensional nanolayers of the bismuth tungstate into a layered heterojunction with a second nanolayer of a different semiconductor. A team led by Professor Lu Jianmei at Soochow University, China, found that black phosphorus may be a suitable partner for bismuth tungstate.
The researchers used black phosphorus consisting of rippled layers of six-membered rings that can be split into individual atomic layers, covering these nanolayers evenly with 50 nm chips of bismuth tungstate. The black phosphorus provided a broad light absorption range, and because the energy levels of the electrons in the two materials are compatible, light-induced positive and negative charges (electron-hole pairs) were efficiently separated, transported within the heterostructure and transferred.
The resulting photocatalytic degradation of NO was significantly more effective than with other bismuth-based materials, said the researchers. However, an additional platinum-based co-catalyst was required to produce hydrogen gas from the breakdown of NO.
The researchers showed that under irradiation, electrons moved through the black carbon-bismuth tungstate heterostructure to the platinum atoms. Thereafter, the electrons rapidly reduce the H+ ions in water to form hydrogen gas. With visible light, the efficiency of the catalytic process was nine times that of pure bismuth tungstate.
The researchers suggest that black phosphorus may have broad applicability that extends to the generation of renewable energy and the treatment of exhaust gases.
The article can be found at: Hu et al. (2019) Z‐Scheme 2D/2D Heterojunction of Black Phosphorus/Monolayer Bi2WO6 Nanosheets with Enhanced Photocatalytic Activities.
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Source: Wiley; Photo: Shutterstock.
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