Driving electrochemical oxygen reduction and hydrazine oxidation reaction by enzyme-inspired polymeric Cu(3,3′-diaminobenzidine) catalyst

Owing to the well-defined molecular structure and tunable mono-, di-or multinuclearity, Cu-N complexes have recently drawn specific attention as emerging catalysts for sustainable electrocatalytic oxygen reduction reaction (ORR) and other reactions. However, compared to state-of-the-art Pt/C, most of these Cu-based molecular catalysts show low catalytic activity due to the intrinsically limited capability and challenges in electronic structure modulation and sequential electron transfer within a single small molecule. Herein, inspired by structure-property relationships of laccases (a type of macromolecular biological catalyst), we report a facile molecular assembly of Cu(3,3'-diaminobenzidine) polymeric complex on carbon black via Cu-N complexing and p-p interaction as a highly efficient bifunctional electrocatalyst for ORR and hydrazine oxidation reaction (HOR), two half reactions for hydrazine fuel cells. Similar to the function of the Cys-His group in natural laccases, the 3,3'-diaminobenzidine ligand in the proposed polymeric catalyst synergistically adjusted the electronic structure of the Cu-N complex center and mediated a multiple-electron transfer cooperatively with carbon black via a long-range p-p interaction, owing to its electron reservation and p-conjugated properties. This study may provide a new way to design highly efficient biomimetic noble-metal-free electrocatalysts with well-defined and tunable structures.