Tribocatalytic degradation of concentrated methyl orange solutions by BiFeO3 nanoparticles prepared through a sol–gel method

With a relatively narrow bandgap of around 2.0 eV, BiFeO₃ (BFO) nanoparticles have been extensively investigated as an appealing visible-light photocatalyst. In this study, BFO nanoparticles prepared through a sol–gel method were explored as a tribocatalyst to degrade methyl orange (MO) solutions. With BFO nanoparticles stimulated through magnetic stirring using Teflon magnetic rotary disks, as much as 100% of 10 mg per L MO and 99% of 30 mg per L MO solutions were degraded after 20 min and 160 min of magnetic stirring, respectively. For reference, TiO₂ nanoparticles (P25) were stimulated under the same conditions and degraded 97% of 10 mg per L MO and 97% of 30 mg per L MO solutions after 150 min and 540 min of magnetic stirring, respectively. The calculated MO degradation rate constants for BFO at concentrations of 10 mg per L and 30 mg per L were 4.94 h⁻¹ and 1.19 h⁻¹, respectively, while the corresponding values for P25 were 0.86 h⁻¹ and 0.40 h⁻¹, respectively. Free radical trapping experiments showed that positive holes are by far the most important active species in the tribocatalytic degradation of MO by BFO. These findings suggest that in addition to its versatile applications, multiferroic BFO is promising for converting mechanical energy into chemical energy through tribocatalysis.