Amorphous NiMS (M: Co, Fe or Mn) holey nanosheets derived from crystal phase transition for enhanced oxygen evolution in water splitting

Abstract

In recent years, two-dimensional (2D) Ni-based bimetallic sulfides have been widely studied for oxygen evolution reaction (OER). However, traditional 2D nanomaterials are easily re-stacked into dense structures or films when manufactured into practical electrodes. Herein, we report an efficient approach to construct amorphous holey NiMS nanosheets (M = Co, Fe, Mn) to overcome this difficulty. Taking amorphous holey NiCoS nanosheets (denoted as holey NiCoS-NS) as a model material, we illustrate the feasibility of this method to control the hole size and pore density in the nanosheets by altering the time of sulfidation process. Benefiting from porous 2D architecture, S-doped species, synergistic effects of Ni and Co, as well as amorphous nature, the holey NiCoS-NS exhibit a low overpotential of 280 mV at current density of 10 mA cm−2 and excellent stability in 1.0 M KOH. By the X-ray photoelectron spectrum (XPS) analysis, this enhanced performance is ascribe to the in-situ generated Ni/Co oxy(hydroxide) active phase during oxygen evolution reaction. Besides, when further employed as a two-electrode electrolyzer assembly, the holey NiCoS-NS exhibits a low potential of 1.58 V at 20 mA cm−2, serving as one of the best water-splitting electrocatalysts to date. This work not only provides a feasible strategy to develop efficient and durable OER catalysts but also represents a general strategy for the structure-performance relationship of 2D transition metal sulfide electrocatalysts.