A Facile Route for Constructing Effective Cu−Nx Active Sites for Oxygen Reduction Reaction

The coordination number between copper and nitrogen in copper/nitrogen-based electrocatalysts is important for boosting the oxygen reduction reaction (ORR). However, it is difficult to control unsaturated copper/nitrogen constructions as well as to compare their ORR performances in similar carbon matrices in a simple yet efficient manner. In this study, we have easily attained two types of Cu+ -N2 and Cu2+ -N4 constructions simply by etching pyrolyzed Cu-doped zeolitic imidazolate framework nanoleaves (Cu-ZIF-L) with sulfuric acid or nitric acid, respectively. X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra were recorded to further confirm the different copper/nitrogen constructions after the different acid treatments. Electrochemical studies have demonstrated that Cu+ -N2 sites are more active in boosting the ORR performance than Cu2+ -N4 sites. Furthermore, Cu-N/C-H2 SO4 , used as an air cathode in a zinc-air battery, exhibited excellent performance and stability.