Nanocluster arrays grown on a graphene Moire on Rh(1 1 1) are an excellent model system that can bridge the materials gap between single crystals and real catalysts. They feature different adsorption sites like edges, kinks, and facets, but are at the same time well-ordered with a small size distribution. Herein, we used platinum nanocluster arrays to investigate the oxidation of sulfur, which is a common catalyst poison, as a possible route to restore the catalyst. We studied the kinetics in a site-resolved manner with high-resolution XPS, despite the complex shape of the nanoparticles. Since SO3 and SO4 were the only observable SOx surface species, the reaction of S to SO was identified as the rate-determining step. As a secondary process, the displacement of sulfur from edge to facet sites caused by oxygen was observed.