Ruthenium Complexes in Homogeneous and Heterogeneous Catalysis for Electroreduction of CO 2

We have studied two structurally related, water‐insoluble ruthenium complexes [Ru II (tpy*)(phenCO 2 )](PF 6 ) ( 1 ) (tpy*=5,4′,5′′‐tri‐tert‐butyl‐2,2′;6′,2′′‐terpyridine; phenCO 2 H=1,10‐phenanthroline‐2‐carboxylic acid) and [Ru II (tpy)(dmphen)(Cl)](PF 6 ) ( 2 ) (tpy=2,2′;6′,2′′‐terpyridine; dmphen=2,9‐dimethyl‐1,10‐phenanthroline, also known as neocuproine) and their electrocatalytic activity for CO 2 reduction in acetonitrile and after immobilization on the reduced graphene oxide (rGO) in water (pH 7.2). Under homogeneous conditions (in CO 2 saturated acetonitrile solution), characteristic major CO 2 reduction waves indicate ∼280 mV lower overpotential upon changing the catalyst from 1 to 2 . The higher CO 2 electroreduction performance of 2 is also reflected on the heterogeneous rGO surfaces.