Hydrogel-Derived Co<sub>3</sub>ZnC/Co Nanoparticles with Heterojunctions Supported on N-Doped Porous Carbon and Carbon Nanotubes for the Highly Efficient Oxygen Reduction Reaction in Zn–Air Batteries
Jianwen Liang, Jinpeng Chen, Guilong Wang, Jingjing Liu, Naiguang Wang, Zhicong Shi
Abstract
It is crucial for metal–air batteries and fuel cells to design non-precious-metal catalysts instead of platinum-based materials to boost the sluggish oxygen reduction reaction (ORR). Herein, Co3ZnC/Co nanoparticles with heterojunctions supported on N-doped porous carbon and carbon nanotubes (CNTs) are fabricated by pyrolyzing the hydrogel prepared from melamine and citric acid chelated with Co2+/Zn2+ ions. This hybrid shows strong ORR catalytic activity as its half-wave potential reaches 0.88 V (vs reversible hydrogen electrode (RHE)) in 0.1 M KOH and Zn–air batteries with the catalyst have higher discharge plateaus and capacity than those employing Pt/C. The hybrid mixed with RuO2 can also be used as an efficient bifunctional catalyst for rechargeable Zn–air batteries. The excellent performance is primarily derived from the Co3ZnC/Co heterojunctions, the electron transfer of which boosts the ORR catalysis. Moreover, the suitable ratio of Co/Zn in precursors results in the epitaxial growth of hollow CNTs and abundant mesopores, hence promoting the adsorption of oxygen and the transport of ORR-related species.