Multifunctional carbon-based metal-free catalysts for advanced energy conversion and storage

Recent advances in research and development of carbon-based metal-free catalysts (C-MFCs) have opened up new research areas for multifunctional electrocatalysis of the oxygen reduction reaction (ORR) in fuel cells, the ORR and oxygen evolution reaction (OER) in metal-air batteries, and the OER and hydrogen evolution reaction (HER) for overall water splitting. New fundamentals governing multifunctional metal-free carbon electrocatalysis were discovered, and recent breakthroughs in this emerging field have enabled C-MFCs to be used as metal-free multifunctional electrocatalysts for various energy-related reactions even beyond the ORR, OER, and HER. This article provides an overview of C-MFCs for multifunctional catalysis, covering their structure design and synthesis and multifunctional catalysis mechanism and potential applications in clean energy conversion and storage, chemical and energy conversion, and environmental protection. Current challenges and future opportunities in this emerging but rapidly developing field are also discussed.