Effects of chemisorption impurities on hydrogen diffusion mechanism from Pd(100) surface into subsurface

Abstract

The impurities exhibit a remarkable impact on adsorption, absorption, and diffusion behavior of hydrogen on catalyst surface, and prompt an essential ongoing challenge on security and development strategy in hydrogen production, separation, purification, and utilization. Given this, S and CO impurities accompanied with or without atomic hydrogen, i.e. S, S + H, CO, and CO + H, were focused to discreetly elucidate their influences on microscopic mechanism for hydrogen travelling into Pd(100) subsurface in terms of spatial orientations and distinct coverages. All viable minimum energy pathways were thoroughly explored by climbing image nudged elastic band method, in which substrate relaxation and reconstruction effects were considered. Quantum results manifest that S or CO overwhelmingly changes structural and electrical properties of metal surface, and thus facilitates hydrogen diffusion, except for ones on H3 site at 0.25 ML coverage. Whereas, H in both S + H and CO + H shows inhibition effect by increasing barrier and blocking active surface site.