Recent Advances in Nanocarbon-Based Nonprecious Metal Catalysts for Oxygen/Hydrogen Reduction/Evolution Reactions and Zn-Air Battery

Abstract

Abstract In this review article, we focus on the design and creation of earth-abundant non-precious metal-coordinated eco-friendly catalysts with high oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performances. The development of a cost-effective, efficient and durable bifunctional ORR and OER electrochemical catalyst is a key for future batteries. So far, precious metals, such as Pt and Ir, have been used as efficient catalysts for the ORR and OER, respectively. However, they are expensive and their deposits on earth are limited, which are the major drawbacks of these metals. One more drawback for the practical application is the sluggish reactions of ORR and OER. Since electroconductivity of promising metal-free catalyst candidates are poor, good electronic supporting materials are needed. Owing to the high conductivity, stability and easy handling, carbon nanotubes are a most promising material. After Introduction, we summarize recent advances in i) carbon nanotube/nanocarbon-based ORR and OER catalysts, ii) metal oxide and others/nanocarbon catalysts for ORR, OER, HER and Zn-air electrodes, as well as iii) computational study for such catalyst reactions. Such studies are highly beneficial for future energy materials design and synthesis in batteries and molecular catalysts with high performances.