Electro- and photo-chemistry of rhenium and rhodium complexes for carbon dioxide and proton reduction: a mini review

Rhenium and rhodium complexes with bipyridyl ligands have been proven to be efficient homogeneous catalysts in the field of carbon dioxide and proton reduction. In this work, the authors provide several examples of these compounds with modified ligand structures and discuss their electro- and photo-catalytic capabilities toward carbon dioxide reduction and NAD⁺ cofactor regeneration. The electrocatalysis is studied by cyclic voltammetry and controlled potential electrolysis for determining the over potentials, Faradaic efficiencies and reaction rate constants. In addition, the photophysics of these compounds is discussed based on UV-visible absorption, photoluminescence and infrared absorption spectroscopy. Results on comparing two different rhenium catalysts for homogeneous photocatalytic carbon dioxide reduction using a sacrificial electron donor are reported.