Tuning the Photocatalytic Activity of Tin Oxide through Mechanical Surface Activation

Tin oxide (SnO₂) nanoparticles were synthesized by the co-precipitation method and mechanically modified by high-energy ball milling. The experimental results demonstrate that the collision with zirconia balls produces slight changes in the crystalline, electronic, morphological, and surface properties of SnO₂, which lead to an increase in the redox potential of the energy level and the formation of the hydroxyl group on the SnO₂ surface. Moreover, these changes are intensified over the milling up to 90 min, directly affecting the photocatalytic performance, which was monitored by the rate of rhodamine B (RhB) degradation driven by ultraviolet (UV) irradiation. As a result, all ground samples showed better photocatalytic activity than pristine SnO₂ (Sn-cop). The maximum degradation of rhodamine B was ca. 75%, achieved with 90 min-milled SnO₂ nanoparticles (Sn-M90), compared to the Sn-cop sample induced a 1.67 times higher degradation rate. The reaction mechanism suggests that its better photocatalytic activity may be associated with the higher increased redox potential of the valence and conduction bands and the formation of hydroxyl active sites on the catalyst surface principal oxidizing agent generated. Therefore, we conclude that the ball milling process is an efficient way to induce stable activation of oxide metal for photocatalytic applications.

Keywords:
SnO₂ nanoparticles; mechanical activation; photocatalysis; bandgap dependence; hydroxyl groups