Oxygen vacancies mediated ultrathin Bi₄O₅Br₂ nanosheets for efficient piezocatalytic peroxide hydrogen generation in pure water

The industrial anthraquinone method for H2O2 production has the serious flaws, such as high pollution and energy consumption. Piezocatalytic H2O2 evolution has been proven as a promising strategy, but its progress is hindered by unsatisfied energy conversion efficiency. Hence, we report the efficient piezocatalytic H2O2 generation in pure water over oxygen vacancies mediated ultrathin Bi4O5Br2 nanosheets (similar to 5 nm). Oxygen vacancies and thin nanostructure not only enhance the piezoelectric properties of Bi4O5Br2, but also advance the separation and transfer of piezoinduced charges. Moreover, density functional theory (DFT) calculations also prove that the introduction of oxygen vacancies enhances the O-2 adsorption and activation ability with largely decreased Gibbs free energy of the reaction pathway. Profiting from these advantages, ultrathin Bi4O5Br2 nanosheets optimized by oxygen vacancies exhibit a prominent H2O2 evolution rate of 620 mu mol g(-1) h(-1) in pure water and 2700 mu mol g(-1) h(-1) in sacrificial system, dominated by a two-step single electron reaction, which exceeds most of reported piezocatalysts. This work demonstrates that oxygen vacancies and ultrathin structure can synergistically enhance the piezocatalytic performance, which presents perspectives into exploring the strategies of defects and nanostructure fabrication for promoting piezocatalytic activity.