Scientists explore the strategies of defects and nanostructure fabrication for promoting piezocatalytic activity

As an important chemical raw material, hydrogen peroxide (H₂O₂) is widely applied in various aspects of industry and life. The industrial anthraquinone method for H₂O₂ production has the serious flaws, such as high pollution and energy consumption. By using ubiquitous mechanical energy, piezocatalytic H₂O₂ evolution has been proven as a promising strategy, but its progress is hindered by unsatisfied energy conversion efficiency.

Bi₄O₅Br₂ is regarded as a highly attractive photocatalytic material due to its unique sandwich structure, excellent chemical stability, good visible light capture ability and suitable band structure. Aspired by its non-centrosymmetric crystal structure, piezoelectric performance has begun to enter the vision of researchers recently.

However, its potential as an efficient piezocatalyst is far from being exploited, especially the impacts of defects on piezocatalysis and piezocatalytic H₂O₂ production over Bi₄O₅Br₂ remains scanty. Thus, mechanical energy-driven piezocatalysis provides a promising method for H₂O₂ synthesis from pure water with great attraction.

Recently, a research group led by Prof. Hongwei Huang from China University of Geosciences reported outstanding piezocatalytic H₂O₂ evolution performance that was achieved over ultrathin Bi₄O₅Br₂ nanosheets with appropriate oxygen vacancies, and disclosed the mechanism that thin structure and oxygen vacancies collectively enhance the piezocatalytic activity.

The results were published in the Chinese Journal of Catalysis.

Ultrathin Bi₄O₅Br₂ nanosheets with controllable oxygen vacancy concentrations are synthesized by a one-step solvothermal method by tuning the water to ethylene glycol ratio. Experiments and theoretical calculations have shown that Bi₄O₅Br₂ with appropriate oxygen vacancies exhibits dramatic performance for piezocatalytic H₂O₂ production.

On the one hand, oxygen vacancies and thin structure largely increase the piezoelectric properties and piezoelectric potential of Bi₄O₅Br₂, which improve the separation and transfer of piezoinduced charges. On the other hand, oxygen vacancies promote oxygen adsorption and activation on the surface of Bi₄O₅Br₂, and lead to constantly decreased Gibbs free energy of the reaction pathway.

Therefore, the piezocatalytic H₂O₂ production performance of Bi₄O₅Br₂ with appropriate oxygen vacancies is higher than that of other commonly used piezocatalysts.