Water-soluble binuclear aquo Cu(ii) complex with an amide ligand as an electrocatalyst for the OER, HER and CO2RR

Abstract

A dinuclear copper complex (1) with the formula Cu₂L₂ (where L = [3-((pyridin-2-ylmethyl)carbamoyl)isonicotinic acid]) was synthesized and characterized by single-crystal XRD and mass spectrometry. The complex showed a high order of electrocatalytic hydrogen evolution reaction (HER) and carbon dioxide reduction reaction (CO₂RR) activity in acidic media, along with a moderate oxygen evolution reaction (OER) activity in the pH range of 7 to 13.5. The efficiency of 1 for the HER was calculated as follows: TOF = 1679 s⁻¹, TON = 586 and F.E. = 83% in 56 equivalents of perchloric acid. For the CO₂RR, a TOF value of 4 h⁻¹, a TON of 18 and an F.E. of 92% were observed, with a percentage selectivity of ∼99.99% for CO₂ to (COOH)₂. The best water oxidation activity was accomplished at pH 13.5 with the following electroanalytical efficacy parameters: TOF = 9 s⁻¹ (peak current method), TOF_FOWA = 31 s⁻¹, TON = 66 and F.E. = 84%. The high stability of the molecular catalyst was analyzed through CV, FESEM, EDX and DLS.