Carbon-based electrocatalysts for sustainable energy applications

Carbon-based materials have multiple advantages including abundant sources, tunable molecular structures, high electronic conductivity, and environmental compatibility. Rapidly growing research interests are focused on carbon materials as electrocatalysts for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER), which are critical for sustainable energy technologies including fuel cells, metal-air batteries, and water electrolyzers. A number of papers in this area have been published. However, there is no systematic review yet covering all the general methods to boost carbon-based electrocatalysts for ORR/OER/HER, and reporting their most recent progress. To eliminate the gap, this contribution gives a timely and comprehensive review of such a rapidly growing field of great significance. This review starts with a brief introduction regarding the fundamentals of carbon-based ORR/OER/HER electrocatalysts and proceeds to summarize various synthesis methods of state-of-the-art carbon materials. Subsequently, the most popular strategies to optimize electrocatalytic properties of carbons are thoroughly reviewed. In addition to metal-free carbons, advances regarding hybridized and self-supported carbon electrocatalysts are discussed. This comprehensive review not only conveys the most recent research progress, but also provides essential ideas and methods that guide the design of high-performance carbon-based electrocatalysts, contributing to their large-scale adoption in sustainable energy applications.