Structure–performance relationships of mechanochemically synthesized piezoelectric catalysts BaTiO3, NaNbO3 and BiFeO3

Abstract

Piezoelectric catalysts were synthesized mechanochemically by converting BaCO₃ and TiO₂ to BaTiO₃, Na₂CO₃ and Nb₂O₅ to NaNbO₃ and Bi₂O₃ and Fe₂O₃ to BiFeO₃. The catalytic reactivity of BaTiO₃, NaNbO₃ and BiFeO₃ was tested using a mechanocatalytic arylation reaction involving 4-nitrobenzenediazonium tetrafluoroborate. The observed activity in the arylation reaction showed a dependence on the abundance of piezoelectrically active anisotropic phases as measured by the pre-edge intensity in XANES spectra of BaTiO₃ and NaNbO₃ and distribution of crystalline phases as measured by XRD for BiFeO₃. A kinetic analysis showed that the reaction over BaTiO₃ was limited by the amount of diazonium salt remaining in the reaction vessel, while the reaction over NaNbO₃ and BiFeO₃ was limited by the generation of electron hole pairs within the piezoelectric structure. This work shows that mechanochemically produced piezocatalysts have superior structural characteristics such as greater relative abundance of anisotropic phases, higher surface areas and smaller particle sizes that led the mechanochemically produced catalysts to outperform piezoelectric commercial counterparts when tested under the same arylation milling conditions.