Nanoconfinement Effects of Ni@CNT for Efficient Electrocatalytic Oxygen Reduction and Evolution Reaction

Abstract

Rechargeable zinc-air batteries have been considered as promising candidates for renewable energy conversion, but the lack of highly efficient and stable electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) has imposed a huge constraint for their application. Herein, we develop an green and facile strategy to synthesize core-shell nanostructured Ni@CNT with Ni nanoparticles (Ni NPs) distributed inside the CNTs via the formation of metal-phenolic networks, in which the tannic acid (TA), a ubiquitous natural polyphenol, was used as capping agents. Profited from the outstanding confinement effects, the Ni@CNT can prominently promote the electric transport, adsorption and concentration of reactants onto the active sites, which can facilitate the reaction kinetics. The spatial encapsulation and separation by the CNT shells can protect the Ni NPs from the self-aggregation and surface oxidation, realizing high dispersity and stability. The developed Ni@CNT hybrid shows the superior performance for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in alkaline. For OER in 1.0 M KOH, the overpotentials for Ni@CNT at the current density of 10 mA cm^-2 is only 280 mV. This work pave an avenue for green, facile and elaborate design of highly dispersed metal supported on carbon materials for energy devices.

Keywords: Bifunctional Electrocatalyst, Confinement Effects, Tannic Acid, Metal-Phenolic Networks