Petal-like Fe x S y /WS 2 Heterojunction Nanosheets as an Electrocatalyst for Highly Effective Hydrogen Evolution Reaction

Developing transition metal sulfide electrocatalysts with high efficiency for hydrogen evolution reaction (HER) are highly expected to promote the development of hydrogen energy. Herein, novel iron tungsten sulfide heterojunction nanosheets (Fe x S y /WS 2 Ns) with a petal-like structure were prepared by a facile hydrothermal method. The prepared petal-like Fe x S y /WS 2 Ns owned a large diameter size of ∼1 μm and a thickness of 8 nm for each flake. The developed Fe x S y /WS 2 Ns exhibited excellent HER activity with an overpotential of 118 mV at 10 mA cm –2 and a low Tafel slope of 87 mV dec –1 in 0.5 M H 2 SO 4, which is much better than that of single Fe x S y and WS 2 (>420 mV at 10 mA cm –2 ). This advanced HER activity is owed to the unique thin structure and more exposed active sites provided by defects between the crystal interface of Fe x S y and WS 2 . Furthermore, the Fe x S y /WS 2 Ns as a bifunctional electrocatalyst could achieve energy-saving water-splitting by replacing the oxygen evolution reaction with the urea oxidation reaction to decrease the applied voltage to 147 mV.