Fabricating 3D ultra-thin N-doped porous graphene-like catalysts based on polymerized amino acid metal chelates as an efficient oxygen electrocatalyst for Zn-air batteries

Abstract

Using metal-free heteroatom-doped carbon material electrocatalysts with high efficiency and low cost for oxygen reduction reaction (ORR) to replace Pt or its alloys is a major task for promoting the reaction efficiency of fuel cells. Here, we report the rational design of three-dimensional (3D) ultra-thin N-doped porous graphene-like carbon (NPC) catalyst based on amino acid zinc chelates containing ligand bonds as both templates and nitrogen sources. During high-temperature annealing treatment, the evaporation of Zn is beneficial to produce a hierarchical porous structure, higher specific surface area and more defect sites. A 3D ultra-thin graphene-like covalently crosslinked polymer with a multilayer network structure was formed by a condensation reaction of amino acid Zn complexes. Under the optimized pyrolysis temperature, the as-obtained NPC-1050 catalyst has a higher defect density and graphitic-N/pyridinic-N ratio, and exhibits an excellent ORR catalytic performance. The half-wave potential, onset potential and limiting current density are 0.878 mV, 0.970 mV and 5.64 mA cm⁻², respectively. In addition, it also showed a competitive performance when compared to commercial Pt/C catalysts in Zn-air batteries. The present route may provide new insights into the synthesis of polypeptide or protein metal complexes, and their application in energy fields.