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

Abstract

Piezocatalysis utilizes mechanical energy to achieve the required charge separation for redox reactions, a promising method for clean H2O2 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 (La0.5Sr0.5FeO3-δ and La0.5Sr0.5CoO3-δ) and Ruddlesden-Popper (R-P) type perovskites (LaSrFeO4-δ and LaSrCoO4-δ) are developed for piezocatalytic H2O2 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 LaSrFeO4-δ exhibits H2O2 yields of 548 (in 10 % ethanol) and 247 µmol g−1h−1 (without sacrificial agent), improved by a factor of 1.14, 4.94, or 21.73 compared to La0.5Sr0.5FeO3-δ, LaSrCoO4-δ, or La0.5Sr0.5CoO3-δ, respectively. The piezoelectricity is an overwhelming factor in determining the H2O2 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 H2O2 formation stems from the efficient O2 reduction via a 2-electron transferring pathway, during which the piezoelectric polarization drives the charge separation and transportation, favoring the redox reactions.