Does the chemical activity of an interstitial hydrogen at surface of solids arise from Pauli repulsion?

Abstract

The surface of solids often exerts a Pauli repulsion on the adsorbed atoms/ions (interstitial and/or substitutional), which markedly changes their properties. And the chemical activity of surface atom/ion increases by this way. In this paper, we focus on the activation of the surface interstitial hydrogen in the hydrogenation. We simply refer it ‘Pauli activation of interstitial H’ for short. We first demonstrate that the Pauli repulsion widely exists on the surface of various solids. Then we briefly introduce our past work published decades ago, which is related with the topics of Pauli activation, including the Schrodinger equation of interstitial/substitutional hydrogen and its solutions. Instead of a simple repeat of our previous work, more physical discussions on the properties of interstitial H are presented to help understanding the new catalysis mechanism more deeply. We find that, the electric dipole of interstitial H induced by Pauli repulsion plays a key role in the catalysis. We point the advantage of this catalytic mechanism. By the way, we give an alternative insight to a long ongoing question in the catalysis study. Experiments show that, the most active component in the hydrogenation is the ‘subsurface hydrogen’ under the surface of transition metals, rather than the ‘surface hydrogen’. We argue that, the ‘subsurface hydrogen’ is just the Pauli-activated interstitial H located under the coverage of the chemisorbed surface-hydrogen.

Keywords

• Heterogeneous catalysis
• Pauli repulsion
• Pauli hole
• Surface/ subsurface hydrogen
• Hydrogenation