Effect of Metal Catalyst Facets on Polyethylene Adsorption

Abstract

Catalytic conversion provides a path for tackling the global problem of plastic waste handling. The product distributions depend on the location of C–C scission on a catalyst, and thus on the conformation of the polymer on the catalyst surface. However, the effects of catalyst surface morphology on polymer melt adsorption are not well understood. Here, we study Pt surfaces of different terminations and polymers of varying chain sizes to probe the impact of terrace width on polyethylene (PE) conformations on the catalyst surface. We parametrize an atomistic force field using density functional theory calculations and perform replica-exchange molecular dynamics simulations on the PE-catalyst systems. We find that the surface morphology alters the conformations of PE. Stepped surfaces favor shorter adsorbed segments but more such segments adsorb per chain. They also induce more ordering in the adsorbed segments than the flat surface, which has implications for the ability of mean-field models to describe polymer adsorption on surfaces and their subsequent reactions. The smaller chains, earlier believed to be entirely adsorbed on the surface, do not do so on stepped surfaces. We discuss the ramifications of these findings for the hydrogenolysis of PE on catalyst metal nanoparticles.