MOF-derived CoS2/WS2 electrocatalysts with sulfurized interface for high-efficiency hydrogen evolution reaction: Synthesis, characterization and DFT calculations

Developing high-efficiency, economical and non-noble-metal electrocatalysts is of great importance to produce hydrogen through hydrogen evolution reaction (HER) in water splitting. Transition metal dichalcogenide has received increasing interests in the application in efficient catalysis, energy conversion and storage. Now, a unique bimetallic sulfide composite (CoS2/WS2) has been prepared by calcination and one-pot hydrothermal method using metal-organic frameworks (MOFs) as precursors. The presence of suitable thioacetamide (TAA) plays a great role in forming the best sulfide interface between CoS2 and WS2 to enhance HER performance. Herein, the overpotential and Tafel slope of as-synthesized CoS2/WS2 at 10 mA cm-2 in 0.5 M H2SO4 medium are obtained as 79 mV and 52 mV dec-1, respectively, which are much lower than those of most non-noble metalbased electrocatalysts. Density Functional Theory (DFT) calculations verify that the bimetallic configuration through the sulfide interface changes the electronic structure, enhances the electrical conductivity and reduces the hydrogen adsorption energy (Delta GH*), effectively accelerating the Heyrovsky step in the HER process. Meanwhile, CoS2/WS2 shows excellent stability in durability tests. The method proposed in this work provides a feasible solution for synthesizing low-cost electrocatalysts.