How Rh surface breaks CO2 molecules under ambient pressure

Abstract

Utilization of carbon dioxide (CO₂) molecules leads to increased interest in the sustainable synthesis of methane (CH₄) or methanol (CH₃OH). The representative reaction intermediate consisting of a carbonyl or formate group determines yields of the fuel source during catalytic reactions. However, their selective initial surface reaction processes have been assumed without a fundamental understanding at the molecular level. Here, we report direct observations of spontaneous CO₂ dissociation over the model rhodium (Rh) catalyst at 0.1 mbar CO₂. The linear geometry of CO₂ gas molecules turns into a chemically active bent-structure at the interface, which allows non-uniform charge transfers between chemisorbed CO₂ and surface Rh atoms. By combining scanning tunneling microscopy, X-ray photoelectron spectroscopy at near-ambient pressure, and computational calculations, we reveal strong evidence for chemical bond cleavage of O‒CO* with ordered intermediates structure formation of (2 × 2)-CO on an atomically flat Rh(111) surface at room temperature.