Quantum Effects Allow the Construction of Two-Dimensional Co3 O4 -Embedded Nitrogen-Doped Porous Carbon Nanosheet Arrays from Bimetallic MOFs as Bifunctional Oxygen Electrocatalysts.

Abstract

In terms of promising candidates for high-performance fuel cells and water splitting electrocatalysts, two-dimensional (2D) materials refer to a class of materials with high electrical conductivity along 2D conducting channels and possessing abundant active sites in the form of surface atoms and edge sites. Herein, we report an ammonia-modulated method for the synthesis of nanosized bimetallic ZnCo-ZIF, and owing to quantum effects, the nanosized ZnCo-ZIF can be transformed into novel 2D nanosheet arrays, which can be used as a bifunctional electrocatalyst. The size of the ZnCo-ZIF crystals can be controlled to less than 10 nm by increasing the ammonia amount. The products from the nanosized particles through calcination have a distinct structure from the microsized nanoparticles owing to quantum effects and appear to be well-aligned 2D mono-crystalline Co3 O4 -embedded nitrogen-doped porous carbon nanosheet arrays (2D-MCo3 O4 -NCNAs). These novel 2D nanosheet arrays lead to large active surface areas, enhanced mass/charge transport capability, numerous active sites, and strong structure stability. When used as bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), the 2D-MCo3 O4 -NCNAs exhibit superior ORR activity as well as efficient OER activity in alkaline electrolyte, in comparison to the state-of-the-art precious metal catalysts.