Heterogeneous catalysts play a pivotal role in the chemical industry. The strong metal-support interaction (SMSI), which affects the catalytic activity, is a phenomenon researched for decades. However, detailed mechanistic understanding on real catalytic systems is lacking. Here, this surface phenomenon was studied on an actual platinum-titania catalyst by state-of-the-art in situ electron microscopy, in situ X-ray photoemission spectroscopy and in situ X-ray diffraction, aided by density functional theory calculations, providing a novel real time view on how the phenomenon occurs. The migration of reduced titanium oxide, limited in thickness, and the formation of an alloy are competing mechanisms during high temperature reduction. Subsequent exposure to oxygen segregates the titanium from the alloy, and a thicker titania overlayer forms. This role of oxygen in the formation process and stabilization of the overlayer was not recognized before. It provides new application potential in catalysis and materials science.

非均相催化剂在化学工业中起着关键作用。影响催化剂活性的强金属-载体相互作用（SMSI）是数十年来研究的现象。但是，缺乏对实际催化系统的详细机械理解。在这里，通过最先进的原位电子显微镜，原位X射线光电子能谱和原位X射线衍射，在密度泛函理论计算的帮助下，在实际的铂-二氧化钛催化剂上研究了这种表面现象。有关现象如何发生的新颖实时视图。在高温还原过程中，厚度受限的还原型二氧化钛的迁移和合金的形成是竞争机制。随后暴露于氧气会使钛与合金隔离，形成较厚的二氧化钛覆盖层。氧在形成过程和覆盖层稳定中的这种作用以前未被认识到。它为催化和材料科学提供了新的应用潜力。