The Mechanism of Sulfur and Accelerator Activation by the Surface Atomic Structure of Zinc Oxide

ABSTRACT Due to the environmental concerns associated with zinc oxide, there is growing momentum toward limiting its usage, particularly in the rubber tire industry. However, reducing ZnO content in tire manufacturing remains a significant challenge, primarily because the activation mechanism of ZnO has not yet been fully elucidated. In this work, three types of ZnO with different surface structures were synthesized, and the activation effects of various atomic structures on ZnO facets toward sulfur and the accelerator N‐cyclohexyl‐2‐benzothiazole sulfonamide (CBS), were studied through experiments and density functional theory calculations, ultimately converging on the same conclusions: Zn 2+ located in the outermost layer of the ZnO (0 0 1) facet can significantly facilitate the cleavage of S‐S bonds in sulfur and N‐S bonds in the accelerator CBS. The ZnO (1 0 0) facet comprises two energetically distinct surfaces: the high‐energy (H‐(1 0 0)) facet, which exposes two‐coordinate zinc, exhibits relatively high surface reactivity and moderately promotes the decomposition of sulfur and CBS; while the low‐energy (L‐(1 0 0)) facet, dominated by three‐ coordinate zinc, which is more prevalent but possesses lower surface reactivity. The prevalence of L‐(1 0 0) reduces the overall activation efficiency of ZnO (1 0 0) for sulfur and CBS decomposition.