Recent advances in trifunctional electrocatalysts for Zn-air batteries and water splitting

The trifunctional electrocatalysis of the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) is of great importance for the development of electrochemical energy storage and conversion technologies such as Zn-air batteries, fuel cells, and overall water splitting. However, these electrocatalytic reactions are limited by sluggish kinetics and high overpotentials. Motivated by the fact that the rational design of trifunctional electrocatalysts is required to achieve high trifunctional activities for high performance energy storage and conversion devices, various chemical strategies have been exploited for the development of advanced trifunctional electrocatalysts. Herein, we present a comprehensive review of the recent progress and the requirements for trifunctional electrocatalysts. We start with a brief description of key fundamental concepts and mechanisms of the ORR, OER, HER, Zn-air batteries, and water splitting. The recent advances in various types of trifunctional electrocatalysts, including noble-metal-based, transition-metal-based, MOF-based, and carbon-based materials, are discussed. The design principles and relationship on the structure-activity-performance are further presented. Finally, the challenge and viewpoints on the future development of advanced trifunctional electrocatalysts are provided toward sustainable energy technologies.