LAUSR

The present report uncovers the borderline between homogeneous and heterogeneous water oxidation catalysis using a family of Ni complexes containing oxamidate anionic type of ligands. In particular, the Ni complex [(L1)NiII]2– (12–; L1 = o-phenylenebis(oxamidate)) and its modified analogues [(L2)NiII]2– (22–; L2 = 4,5-dimethyl-1,2-phenylenebis(oxamidate)) and [(L3)NiII]2– (32–; L3 = 4-methoxy-1,2-phenylenebis(oxamidate)) have been prepared and evaluated as molecular water oxidation catalysts at basic pH. Their redox features have been analyzed by means of electrochemical measurements revealing a crucial involvement of the ligand in the electron transfer processes. Moreover, the stability of those complexes has been assessed both in solution and immobilized on graphene-based electrodes at different potentials and pHs. The degradation of the molecular species generates a NiOx (Niquel oxides of general formula NixOyHz) layer, whose stability and activity as water oxidation catalyst have also been established...