Homogeneous redox catalysed reduction of CO2 by nickel cyclam catalyst and chromium-based redox mediator

Abstract

The electrochemically decoupled reduction of CO₂ using nickel cyclam as a homogeneous catalyst and chromium propanediaminetetraacetate (PDTA) as a reductive redox mediator is reported in aqueous media. Uniquely, the Ni cyclam catalyst, known for exclusive homogenous CO production instead gives a mixed product selection of HCOO(H) and CO depending on the supporting electrolyte composition, with KHCO₃ favouring CO and KCl favouring HCOO(H). The CrPDTA shows no conventional electrochemical booster effects, but exclusively reacts with the Ni cyclam when generated as a bulk Cr(II) species.