In many surface reactions, also different, competing reaction pathways are possible, and the dominant pathway will depend on the catalyst material and on the reaction conditions. As an example, it is widely agreed that CO oxidation on noble metal surfaces / catalysts will follow a LH mechanism , while on oxide supported Au nanoparticle catalysts, where O2 dissociation on the Au nanoparticles is strongly hindered, a Au-assisted MvK mechanism had been proposed .