Research progress of carbon nanofiber-based precious-metal-free oxygen reaction catalysts synthesized by electrospinning for Zn-Air batteries

Development and utilization of environmentally friendly and renewable energy devices are forced by the increasingly serious energy and environmental crisis. Zn-air batteries (ZABs) have been regarded as efficient energy devices due to the high energy density and safety, so it is very important to develop bifunctional oxygen reaction catalysts for air-cathodes. Electrospinning has attracted great attention in design and synthesis of 1D carbon nanofiber-based precious-metal-free oxygen catalysts for ZABs. This work aims to systematically summarize the research progress of electrospinning for fabricating carbon nanofiber-based precious-metal-free catalysts as air-cathode for ZABs. Firstly, a brief introduction of oxygen reaction mechanisms for air-cathodes is provided. Then, the structural characteristics and performance of the metal-free nanofiber, transition metal-based nanofiber and other precious-metal-free nanofiber catalysts used in ZAB are reviewed. Finally, the designed principle of carbon nanofiber catalysts prepared by electrospinning are highlighted. The challenges and future prospects on the development of carbon nanofiber-based precious-metal-free catalysts for ZABs are presented. This review can provide a comprehensive understanding the application of electrospinning in ZABs and lay a foundation for the design of high-performance air-cathodes.