FeS2 crystal lattice promotes the nanostructure and enhances the electrocatalytic performance of WS2 nanosheets for the oxygen evolution reaction

Abstract

The control of surface elements and nanostructures is one of the effective ways to design and synthesize high performance catalysts. Herein, we, for the first time, prepare FeS₂ crystal lattices on WS₂ nanosheets (FeS₂ CL@WS₂ NS) by solvothermal methods for the oxygen evolution reaction (OER). The FeS₂ CLs effectively prevent the oxidation and aggregation of WS₂ nanosheets and increase the electrochemically active surface area. The abundant surface defect in the FeS₂ CL@WS₂ NS electrocatalyst reduces the stress between the crystal lattices of FeS₂ and that of WS₂. The overpotential (260 mV) of the FeS₂ CL@WS₂ NS electrocatalyst for the OER at a current density of 10 mA cm⁻² is superior to those of WS₂ NS/Ni foam (310 mV) and IrO₂/Ni foam (300 mV) in 1.0 M KOH solution. An electrochemical–kinetic study shows that the Tafel slope of 54 mV per decade for the FeS₂ CL@WS₂ NS electrocatalyst is lower than those of WS₂ NS (102 mV per decade) and IrO₂/Ni foam (77 mV per decade). In addition, the charge transport resistor (2.3 Ω) of the FeS₂ CL@WS₂ NS electrocatalyst for the OER is smaller than that of WS₂ NS. These faster kinetic properties, in turn, explain the high catalytic activity of the FeS₂ CL@WS₂ NS electrocatalyst for the OER. The XPS and HRTEM results of the post stability sample confirm that Fe²⁺ and W⁴⁺ are oxidized after durability measurement. Thus, we think that the FeS₂ CL@WS₂ NS electrocatalyst is a promising candidate for efficient, low-cost, and stable non-noble-metal-based OER electrocatalysts.