Utilization of a dicopper(II) complex of tetrapyridyl ligand as the precursor for the synthesis of copper-based composites and their catalysis

Abstract Herein reported are the catalytic properties of the composites derived from complex [Cu 2 (tpbn)(CH 3 OH) 4 (ClO 4 ) 2 ](ClO 4 ) 2 ( 1 ) of tetrapyridyl ligand N,N,N′,N′-tetrakis(2-pyridyl-methyl)-1,4-butanediamine (tpbn). Complex 1 was a precursor of the composites catalytically active for water oxidation and CO 2 reduction reactions. Under the anodic potential of +1.20 V vs. Ag/AgCl, composites deposited on tin-doped indium oxide (ITO) electrodes from the solutions of complex 1 at pH 9.0–13.5 are highly active for water oxidation reaction (WOR). In contrast, under the cathodic potential of −1.20 V vs. Ag/AgCl, the species deposited on the copper surface from the solutions of complex 1 at pH 6.7 can efficiently catalyze CO 2 reduction to CO. Scanning electron microscopy (SEM) showed that the composites on ITO and Cu surfaces were particulate materials. X-ray photoelectron spectroscopy (XPS) and x-ray-excited Auger electron spectroscopy (XAES) analysis revealed that the composites mainly contain cuprous oxide (Cu 2 O) and copper oxide (CuO) in different ratios, which showed different catalytic activity to water oxidation and CO 2 reduction reactions in copper-free aqueous solutions under low overpotentials. This work demonstrated that metal complexes are good candidates for preparing robust, noble-metal-free catalysts for reactions relevant to renewable energy sources.