l-Lysine-induced green synthesis of CoS/Co3O4 nanoframes for efficient electrocatalytic oxygen evolution

Abstract

The Co-based heterojunction is regarded as an efficient material for the oxygen evolution reaction (OER), but the synthesis is still time- and labor-consuming, and environmentally unfriendly. Herein, we propose a green and facile L-lysine-induced strategy for the successful synthesis of porous CoS/Co₃O₄ nanoframes (NFs). L-Lysine played a pivotal role in facilitating the formation of the stable Co(OH)₂ nanosheet precursor, which was subsequently in situ converted into CoS/Co₃O₄ NFs through the sulfuration treatment. The resulting CoS/Co₃O₄ NFs showed a low overpotential of 304 mV at 10 mA cm⁻² and remarkable long-range durability in 1.0 M KOH for the OER. The rechargeable Zn–air battery exhibited high charge–discharge cycling stability (>120 h) with CoS/Co₃O₄ NFs + Pt/C as an air cathode. Density functional theory calculations demonstrated that the charge density of the CoS/Co₃O₄ heterostructure can be redistributed by rebalancing the Fermi level after the contact between CoS and Co₃O₄, potentially modulating the pristine catalytic properties of single components. This work provides a facile and green synthesis strategy for developing efficient Co-based catalysts in sustainable energy conversion devices.