Design of earth-abundant ternary Fe1−xCoxS2 on RGO as efficient electrocatalysts for hydrogen evolution reaction

Developing inexpensive and earth-abundant materials instead of precious metal Pt has broad applications in the production of hydrogen through electrolysis of water. Herein, a series of ternary Fe1−xCoxS2 nanoparticles hybridized with reduced graphene oxide (RGO) (Fe1−xCoxS2/RGO) have been synthesized by a facile hot-injection method for hydrogen evolution reaction (HER) in acidic solutions. The electrochemical measurements show that the optimal HER activity is obtained when the ratio of Co is 61%, exhibiting a low overpotential of 198 mV at 10 mA cm−2 and a small Tafel slope of 94 mV dec−1. Moreover, density-functional theoretical calculations indicate that the incorporation of Co atoms can activate the electrocatalytic performance of FeS2 with a smaller Gibbs free energy for hydrogen adsorption (ΔGH*). The enhanced HER activity might be owing to the synergistic effects between the highly conductive RGO supports and the electroactive Fe0.39Co0.61S2. This study gives an insight into the design and development of the HER electrocatalysts based on earth-abundant Fe1−xCoxS2 and promotes the applications of transition metal dichalcogenides for hydrogen generation in the future.