The general electronic principle driving size-dependent surface chemical activities of nanomaterials

TL;DR

This paper uncovers a general electronic principle explaining how the size of nanomaterials influences their surface chemical activities through orbital redistribution and potential, combining experimental and theoretical approaches.

Contribution

It introduces a new electronic principle and a mathematical model linking size-dependent surface activities to orbital potential and structural factors.

Findings

Orbital redistribution is key to surface chemical interactions.

Size inversely correlates with orbital potential.

Structural factors like defects amplify size effects.

Abstract

Size can widely affect the surface chemical activities (SCAs) of nanomaterials in chemisorption, catalysis, surface effects, etc., but the underlying electronic nature has long remained mysterious. We report a general electronic principle that drives the origin of size-dependent SCAs by combining experimental probing and theoretical modeling. Using the chemisorption of H2O2 on TiO2 as a model reaction, we experimentally reveal that the central electronic process of surface chemical interactions lies in the competitive redistribution of surface atomic orbitals from energy band states into surface coordination bonds. By defining orbital potential, a site-dependent intrinsic electronic property that determines surface activities, we further establish a mathematical model to uncover the physical nature of how structural factors correlate to SCAs, particularly the roles of size. We discover that the electronic nature of size effect lies in its inverse correlation to orbital potential and amplification effect on other structural factors like defects and coordination numbers.