Abstract
The lack of highly efficient, inexpensive catalysts severely hinders large-scale application of electrochemical hydrogen evolution reaction (HER) for producing hydrogen. MoS2 as a low-cost candidate suffers from low catalytic performance. Herein, taking advantage of its tri-layer structure, we report a MoS2 nanofoam catalyst co-confining selenium in surface and cobalt in inner layer, exhibiting an ultra-high large-current-density HER activity surpassing all previously reported heteroatom-doped MoS2. At a large current density of 1000 mA cm−2, a much lower overpotential of 382 mV than that of 671 mV over commercial Pt/C catalyst is achieved and stably maintained for 360 hours without decay. First-principles calculations demonstrate that inner layer-confined cobalt atoms stimulate neighbouring sulfur atoms while surface-confined selenium atoms stabilize the structure, which cooperatively enable the massive generation of both in-plane and edge active sites with optimized hydrogen adsorption activity. This strategy provides a viable route for developing MoS2-based catalysts for industrial HER applications.
Highlights
The lack of highly efficient, inexpensive catalysts severely hinders large-scale application of electrochemical hydrogen evolution reaction (HER) for producing hydrogen
As shown in scanning electron microscopy (SEM) (Fig. 1a) and transmission electron microscopy (TEM) (Supplementary Fig. 1) images, the Se-MoS2 nanofoam (MoS2-NF) possesses a nanofoam morphology with abundant spherical cavities, which will favor the mass transportation of reactants to access more active sites of the catalyst[15,19,21,26]
Se-doping prominently stabilizes the Co-doped basal plane and edges by forming Co–Se bonds (Fig. 5c, d), where the formation energies of Co/Se-codoped basal plane, Mo-edge, and S-edge can be reduced by 0.21, 0.12, and 0.07 eV per Co–Se bond formed, respectively, compared with those with Co and Se separated from each other. These results demonstrate a synergy between the activating effect of inner-layer Co-doping and the stabilization effect of surface Se-doping in the Co/Se-codoped MoS2, which significantly improves the HER performance by simultaneously enriching active sites and optimizing their hydrogen adsorption activities
Summary
The lack of highly efficient, inexpensive catalysts severely hinders large-scale application of electrochemical hydrogen evolution reaction (HER) for producing hydrogen. Combined with a morphology-controlling method of fabricating three-dimensionally nanofoam architecture to promote edge formation, the massive generation of both inplane and edge active sites are achieved in the synthesized MoS2 nanofoam with co-confined Co and Se atoms (Co/Se-MoS2-NF) Such a catalyst exhibits a high HER activity at large current densities, which, to the best of our knowledge, surpasses those of all previously reported heteroatom-doped MoS2 catalysts and even the commercial precious Pt/C catalyst in acidic electrolyte. Density functional theory (DFT) studies demonstrate a synergy between the activating effect of confining Co in the inner Mo-layer and the stabilizing effect of confining Se in the surface S-layer, which promotes the formation of both in-plane and edge active sites and optimizes the adsorption free energies of hydrogen This strategy opens up a new prospect of tailoring the catalytic performance of MoS2 toward large-scale HER applications through confining multielements in different layers
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