Two-Dimensional Amorphous Cobalt Oxide Nanosheets/N-Doped Carbon Composites for Efficient Water Splitting in Alkaline Medium

Abstract

The development of earth-abundant, inexpensive, and durable noble-metal-free bifunctional electrocatalysts is important to design anion exchange membrane water electrolyzers (AEMWEs). In recent years, tremendous efforts have been carried out to prepare two-dimensional (2D) amorphous noble-metal-free catalysts for alkaline water splitting as they have unique characteristics in catalysis. In this report, a 2D amorphous cobalt oxide nanosheet/nitrogen-doped carbon composite (CoOx/CNx) was prepared for water splitting in the base. The catalyst displays excellent oxygen evolution reaction (OER) activity with 310 mV overpotential at 10 mA/cm2 current density and 60.7 mV/dec Tafel slope value. The CoOx/CNx also shows very good long-term OER stability in the base. The CoOx/CNx composite also shows moderate hydrogen evolution reaction (HER) activity, and the activity increases with increasing reaction time. We demonstrate that the HER activity increases with increasing HER cycle because of the surface modification of the catalyst. The CoOx/CNx also shows excellent overall water-splitting activity as well as durability. The catalyst possesses high catalytic activity because of its 2D, amorphous sheetlike morphology, strong synergistic interactions, porosity, large electrochemical surface area, and easy access to abundant active sites. Thus, this result may offer a prospect to design a noble metal-free electrocatalyst for AEMWEs and other renewable energy-based devices.