CHAPTER 8: Electrochemistry Reactions Catalyzed by Metal-free Functionalized Carbons

Electrochemical reactions, such as the oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), have attracted tremendous interest recently due to their pivotal roles in next-generation energy technologies, including water splitting, fuel cells, metal–air batteries, etc. As promising alternatives to noble-metal-based electrocatalysts, metal-free functionalized carbons are of progressively increasing importance attributed to their low cost, effective activity and remarkable durability. However, there remains a great challenge to fully boost the performance of metal-free functionalized carbons in spite of the achievements in material synthesis and understanding of the mechanism. In this chapter, we will highlight some critical and representative developments in this field, aiming at a concise and clear summary of the underlying mechanism and also some essential insights for targeted optimization. As metal-free nanocarbon catalysts are more intensively researched for the ORR, we primarily focus on the ORR to discuss the different activity origins, including dopants, edges, and defects. The development of functionalized carbon materials for OER catalysts, including N-doped, oxidized, and dual-doped carbons, are then discussed. Especially, the applications of metal-free functionalized carbons as multifunctional catalysts for the ORR, OER or HER are also included. This is expected to promote the rational design of metal-free functionalized carbon catalysts for the ORR, OER, HER, and other important electrochemistry reactions for sustainable energy.