Study on Performance and Mechanism of the Ball-Milling-Driven Piezoelectrochemical Effect on Catalytic Oxidation of Toluene in the Air Condition

We use the characteristics of piezoelectric barium strontium sulfate (BSS) to collect the mechanical energy generated by ball-milling to produce the piezoelectrochemical effect. At the same time, in coordination with the mechanochemical effect generated by ball-milling, toluene is oxidized to phenol in air atmosphere. Starting with characterization, BSS was characterized by X-ray powder diffraction (XRD), thermal field emission scanning electron microscopy, electrochemical test, Fourier transform infrared spectroscopy, and ultraviolet visible spectroscopy. Moreover, six reaction parameters─catalyst type, catalyst dosage, reaction time, ball-milling speed, pH value of reaction solution, and toluene concentration─were discussed, and the optimum reaction conditions were obtained. Ultimately, the mechanism of catalytic reaction was discussed. It is found that the superoxide radical (•O2–), which formed by oxygen in the air and electrons generated by the BSS piezoelectric effect, is the main oxidation species for the oxidation of toluene. The oxidation potential of •O2– is −0.33 V versus NHE, which can oxidize toluene to phenol without excessive oxidation.