Single Zn atoms and hierarchical pore architecture jointly improve oxygen reduction electrocatalysis

Abstract

Investigations on high-efficiency single atom catalysts (SACs) for oxygen reduction reaction (ORR) have aroused widespread concern, particularly for transition metals. However, the inherent catalytic performance is greatly affected by metal types and pore structure of carbon substrates. Herein, a non-noble Zn-based single-atom electrocatalyst (Zn-N-C) is proposed and confirmed that atomically dispersed Zn is anchored onto the amply micro/mesoporous support decorated with nitrogen doping. Benefit from the pore structure and single-atom site, Zn-N-C reveals superior ORR behavior with high E_1/2 (0.874 V) and low Tafel slope (68.8 mV dec^-1) in 0.1 M KOH, markedly surpassing state-of-the-art Pt/C. EXAFS and DFT results show that Zn-N₄ coordination configuration decreases the free energies of oxygen-containing intermediates (*OOH and *OH) and the theoretical overpotential is as low as 0.45 eV. As a result, the self-assembled Zn-air battery performs well in peak power density (226.4 mW cm⁻²), specific capacity (746.4 mAh g⁻¹) and long-term durability.