Cr doped-Co9S8 nanoarrays as high-efficiency electrocatalysts for water splitting

Abstract

Doping transition metal ions into Co9S8 has received extensive attention as an electrocatalyst for water splitting. In this paper, Density functional theory (DFT) calculation is supposed to assess the water adsorption energy of M (M = 1-Cr, 3-Cr and 6-Cr) doped CoxS8 to better predict the water oxidation activity of all the synthetic materials and synergistic reaction mechanism between the content of doped Cr ion and cobalt ion. A series of Cr-CoxS8 materials are firstly prepared by simple hydrothermal and sulfuration process. It is worth noting that only 1.45 V cell voltage is required to generate 10 mA cm−2 current density during the whole water splitting, which is one of the smallest cell voltages reported. The experimental results are highly consistent with theoretical predictions. The excellent electrochemical activity of Cr3–Co6S8/NF is mainly ascribed to the following factors: firstly, the presence of Cr3+ enhances the chemisorption free energy of water and the metallic nature of the material. Secondly, the rough surface around the honeycomb nanoarrays further improves the reaction surface area and promotes mass transfer rate. The work offers a new insight for developing an environmentally friendly and robust electrocatalyst for large-scale water splitting applications.