The sluggish reaction kinetics at the oxygen cathode is one of the important issues hindering the commercialization of the metal-air batteries. Although the noble metal can be used as the high-efficiency electrocatalyst to solve the problems to some extent, the high cost and scarcity of these noble-metal catalysts have limited their application in electrocatalysis. In this review, we discussed the mechanisms of the ORR and OER, and proposed the principles for the bifunctional electrocatalysts firstly, and then the state-of-the-art bifunctional catalysts, including carbon-based materials and transition-metal-based materials. On the basis of that, the self-supporting 3D noble-metal-free bifunctional ORR/OER catalysts were also discussed. Finally, the perspectives for the bifunctional electrocatalysts were discussed.

氧正极反应动力学缓慢是阻碍金属空气电池商业化的重要问题之一。虽然贵金属可以作为高效电催化剂在一定程度上解决上述问题，但这些贵金属催化剂的高成本和稀缺性限制了其在电催化中的应用。在这篇综述中，我们讨论了 ORR 和 OER 的机理，并首先提出了双功能电催化剂的原理，然后提出了最先进的双功能催化剂，包括碳基材料和过渡金属基材料。在此基础上，还讨论了自支撑3D无贵金属双功能ORR/OER催化剂。最后，讨论了双功能电催化剂的前景。