Mechanistic Investigation into Tribocatalysis: Insights from Anatase and Rutile TiO₂

Abstract

Overall, the current research on the friction catalysis mechanism mainly focuses on two explanations: electron transfer and electron transition. However, the mechanism of electron transition has always been a speculative concept, lacking direct proof and evidence. In this study, the direct bandgap anatase and the indirect bandgap rutile were utilized for the friction catalytic degradation of rhodamine at concentrations of 100, 300, and 500 respectively. The mechanism of friction catalysis was then investigated and elucidated. TiO2 with anatase structure is indirect bandgap semiconductor. Due to this, the electrons and holes excited by friction catalysis do not easily recombine, thus exhibiting excellent friction catalytic performance. For a 500 concentration of rhodamine dye approaching the actual concentration of industrial dyes, the anatase structure TiO2 has a degradation rate of 100% after 25 h. However, for the rutile anatase structure of TiO2, since it is a direct bandgap semiconductor, the recombination of excited electrons and holes occurs, and the degradation rate of the rhodamine dye at a 500 mg/L is almost 20% after 25 h. This result provides a more favorable experimental proof and evidence for the electron transition facilitated by friction, and will undoubtedly offer theoretical and experimental references for future research on friction catalysis. This investigation will help us gain a deeper understanding of the catalytic mechanism and principles of friction-induced catalysis.