Precise regulation of pyrrole-type single-atom Mn-N4 sites for superior pH-universal oxygen reduction

Abstract

The study of atomically dispersed metal-nitrogen electrocatalysts is still limited in terms of understanding their catalytic mechanism because of the inability to precisely regulate the coordination number and type of N in combination with the metal elements. Inspired by the high catalytic activity and selectivity of natural enzymes, herein, we have designed and fabricated ultrathin carbon nanosheet-supported Mn single-atom catalysts (SACs) with a precise pyrrole-type Mn-N4 (PT-MnN4) configuration using a bio-mimicking strategy. The PT-MnN4 SACs display outstanding oxygen reduction reaction (ORR) activity, with a half-wave potential (E1/2) of 0.88 V (vs. revisible hydrogen electrode [RHE]) and extremely high stability in alkaline media. Moreover, superior ORR activities are also obtained, E1/2 of 0.73 V and 0.63 V in acid and neutral electrolytes, respectively, indicating the efficient pH-universal ORR performances. The assembled zinc–air battery using the PT-MnN4 SACs as air cathodes exhibits a high peak power density (175 mW cm−2) and long-term stability up to 150 h, implying its promising application in metal–air batteries. This study has paved the way toward the rational design and precise regulation of single-atom electrocatalysts.