Gram-Scale Preparation of 2D Transition Metal Hydroxide/Oxide Assembled Structures for Oxygen Evolution and Zn-Air Battery

Abstract

Construction of 2D materials into a hierarchical structure cannot only effectively avoid restacking of individual nanosheets but also endows them with improved catalytic efficiency, which have generated extensive interest in recent years. Nevertheless, the scalable and effective preparation of 2D materials constructed hierarchical structures, such as unique 2D/1D structure, is rarely achieved. Herein, we report a facile alkali-soaking strategy for the preparation of 2D transition metal hydroxide/oxide nanosheets-assembled hierarchical structures, in which the rational designed bimetallic metal–organic frameworks (MOFs) are annealed followed by a simple alkali soaking. Our method is capable of preparing various hierarchical structures based on 2D materials, including Co(OH)2, Ni(OH)2, and Mn3O4 nanosheets. Moreover, a high yield of ∼2.2 g was achieved for a batch of Co(OH)2 nanosheet-assembled structure. Impressively, the as-synthesized Co(OH)2 hierarchical structure shows excellent electrocatalytic performances toward the oxygen evolution reaction (OER), which achieves a current density of 10 mA cm–2 at a low overpotential of 267 mV with a small Tafel slope of 62.0 mV dec–1. Furthermore, it delivers a small charging/discharging voltage gap of 1.2 V at 75 mA cm–2 and high stability for over 240 h, when used as an air cathode for rechargeable Zn-air batteries.