N-Doped Graphene-like Carbon Nanocages Modified by Trace Nickel Species for Efficient ORR and OER Bifunctional Electrocatalyst

As a new class of catalytic materials with excellent performance, nitrogen (N)-doped carbon nanocages with high surface reactivity have extremely broad application prospects in electrocatalysis. In this study, N-doped graphene-like carbon nanocages (NGCNs) modified by trace nickel (Ni) species (possible components are: single atoms and clusters) were prepared from nickel acetate, a carbon source and a nitrogen source by thermal decomposition and acid etching methods. The excess Ni was removed by acid etching, and finally a three-dimensional (3D) NGCNs-supported atomic nickel catalyst was obtained. Then, the catalyst was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). At the same time, the 3D NGCNs-supported atomically dispersed nickel catalyst was assembled into oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrodes for electrochemical evaluation in 1 M KOH alkaline electrolyte, and the possible synergistic effect between Ni single atoms and Ni clusters, as well as between N-doped carbon frameworks and Ni species in NGCNs, was also suggested.