Porous carbon nanosheets for oxygen reduction reaction and Zn-air batteries

Zn-air batteries (ZABs) are a promising source of renewable energy for portable electronic devices and automobiles because of low-cost and high energy density. The efficiency of ZABs significantly relies on the oxygen reduction reaction (ORR) in air cathode, development of efficient electrochemical catalysts is kindly important. In the past decade, inspired by graphene, porous carbon nanosheets (PCNs) have been widely developed and studied in the field of energy conversion and storage due to their adjustable structure, good and long-distance conductivity, rich porosity, and abundant active sites, as well as excellent performance. In this review, various rational preparation methods toward PCN-based catalysts are summarized. Then, the catalytic active sites in PCNs are classified, and the relationship between performance and active sites are discussed. At the end of this review, the challenges and future prospects for rational development of two-dimensional porous carbon-based electrochemical ORR catalysts as air cathode for ZABs are discussed. This review will give guideline for the development of novel porous carbon-based materials for energy conversion and storage.