Balancing the piezoelectric coefficient and carrier concentration of Bi₂WO_6−x for ultrahigh piezocatalysis

Balancing the piezoelectric coefficient and carrier concentration of materials is key in the field of piezocatalysis. In this work, Bi₂WO₆ material with both piezoelectric and semiconductor properties was chosen as a model material. A one-step ethylene glycol (EG)-assisted solvothermal method was used to synthesize Bi₂WO₆ with oxygen vacancies. By controlling the solvothermal time and temperature, the oxygen vacancy concentration (C_OV) was regulated. As C_OV increases, the piezoelectric coefficient decreases, the carrier concentration increases, and the hydrogen production rate first increases but then decreases. When C_OV reaches 1.45×10¹² spins·mg⁻¹, the corresponding piezoelectric coefficient and carrier concentration are 13.9 pm·V⁻¹ and 2.90×10²⁰ cm⁻³, respectively. The optimal hydrogen production rate per power of 2.21 μmol·g⁻¹·h⁻¹·W⁻¹ is equivalent to or even better than that of most reported piezocatalysts. The piezoelectric coefficient and carrier concentration, as two factors, jointly determine the piezocatalytic performance. The findings of this research can provide important and deep-seated insights for better piezocatalysts in the future.