Insight into Size- and Metal-Dependent Activity and the Mechanism for Steam Methane Re-forming in Nanocatalysis

Abstract

Systematic and in-depth understanding of size- and metal-dependent activity plays a pivotal role in nanocatalysis for rational design of highly efficient catalysts. Herein, we report an approach combining microkinetic modeling with a truncated octahedron model to explore the size- and metal-dependent activity, using steam methane re-forming on metallic (M = Rh, Ni, Pt, and Pd) nanoparticles as a model system. It is found that activity is inversely proportional to particle size, and this size-dependent activity results from the fraction change in surfaces with distinct activity. M(211) is the active surface, and the increased M(211) surface fraction with decreasing particle size results in enhanced activity. In addition, the metal-dependent activity is elucidated, with the activity following Rh > Ni > Pd ∼ Pt. Moreover, the intrinsic size- and metal-dependent activity are analyzed on the basis of dominant reaction pathway, which are fundamentally related to C-metal and O-metal binding ability, respectively.