Theoretical investigation on catalytic electrooxidation of CO by RhIII complexes: insight from molecule–surface interaction

Abstract Some RhIII complexes with planar ligands exhibit high catalytic activity in the electrochemical oxidation of CO. However, the mechanism is unclear, and physical-chemical studies are necessary to design complexes. In this study, we experimentally confirmed that the activity of RhIII phthalocyanine on graphite is significantly lower than other complexes, and investigated this difference theoretically. The RhIII-phthalocyanine/graphite has nonbonding orbitals even in the unoccupied region and too deep lowest unoccupied energy level, whereas the other complex/graphite systems with high catalytic activity has bonding orbitals and their orbital levels are not so deep. This study demonstrates the importance of optimizing complex–support interactions.