A Si(111)-(7 × 7) surface as a natural substrate for identical cluster catalysts

Abstract

Large-scale production of metal clusters with definite size and geometry is highly desirable for industrial catalysis, which requires substrates with an exquisite surface structure to uniformly disperse and anchor the clusters. However, synthesis of such templates with artificial holey structures and suitable binding capability is still challenging. For the first time, herein we demonstrate that the Si(111)-(7 × 7) surface is an ideal substrate to prepare subnanometer identical clusters consisting of group-VIIB, VIII, IB and IIB elements for catalysis. This commonly available semiconductor surface intrinsically harbors homogenous and high-density active sites to disperse metal atoms and to assemble identical clusters. As a prototype reaction, the CO₂ reduction reaction on identical metal clusters on the Si(111)-(7 × 7) surface has been explored by using ab initio calculations. We found that the Pd₆ cluster on Si(111)-(7 × 7) is capable of selectively converting CO₂ to high-value C₂–C₄ hydrocarbons and alcohols. The spatially confined hexatomic metal centers simultaneously fix multiple CO₂ molecules and provide exclusive reaction channels that sterically and electronically facilitate C–C coupling. These results offer a facile strategy to obtain and utilize identical metal clusters for practical clean energy production.