Comparative investigation of piezocatalysts composed of La, Sr and Co (Fe) complex oxides in Ruddlesden-Popper type or simple single perovskites for efficient hydrogen peroxide generation

Piezocatalysis utilizes mechanical energy to achieve the required charge separation for redox reactions, a promising method for clean H 2 O 2 production. However, the efficiency of conventional piezocatalysts is limited by the undesirable low piezoelectricity. Herein, novel piezocatalysts composed of La, Sr, Co (Fe) in simple single perovskites (La 0.5 Sr 0.5 FeO 3-δ and La 0.5 Sr 0.5 CoO 3-δ ) and Ruddlesden-Popper (R-P) type perovskites (LaSrFeO 4-δ and LaSrCoO 4-δ ) are developed for piezocatalytic H 2 O 2 production. Results indicate that Fe-containing catalysts outperform Co-containing counterparts and the unique R-P perovskite oxides demonstrate significantly enhanced piezocatalytic performance than the corresponding single perovskites. For example, via piezocatalysis, the LaSrFeO 4-δ exhibits H 2 O 2 yields of 548 (in 10 % ethanol) and 247 µmol g −1 h −1 (without sacrificial agent), improved by a factor of 1.14, 4.94, or 21.73 compared to La 0.5 Sr 0.5 FeO 3-δ , LaSrCoO 4-δ , or La 0.5 Sr 0.5 CoO 3-δ , respectively. The piezoelectricity is an overwhelming factor in determining the H 2 O 2 generation. Furthermore, the piezoelectricity and oxygen vacancy (OV) content is well correlated. The R-P phase with lower OV exhibits a higher piezoelectricity because of the eliminated pining effect to the polarization domain reversion. Mechanism exploration suggests that H 2 O 2 formation stems from the efficient O 2 reduction via a 2-electron transferring pathway, during which the piezoelectric polarization drives the charge separation and transportation, favoring the redox reactions.