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A Facile Way to Construct Effective Cu-Nx Active sites for Oxygen Reduction Reaction.

The coordination number between copper and nitrogen in copper-nitrogen based electrocatalysts is quite important for boosting the oxygen reduction reaction (ORR). However, it is difficult to control the unsaturated copper-nitrogen constructions as well as compare their ORR performance in a similar carbon matrix by a simple but efficient way. Herein, we easily attained two types of Cu + -N 2 and Cu 2+ -N 4 constructions just by etching the pyrolyzed Cu-doped zeolitic imidazolate framework nanoleaf (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 adopted to further confirm the different copper-nitrogen constructions after different acid treatment. By comparison, electrochemical studies demonstrate that Cu + -N 2 sites get higher activity for boosting the ORR performance than that of Cu 2+ -N 4 sites. Furthermore, Cu-N/C-H 2 SO 4 acted as air cathode in the Zinc-air battery exhibits an excellent performance and stability.