Morphology modification of MoS2 by Co doping for highly efficient hydrogen evolution over full pH range at large current density

Abstract

Molybdenum disulfide (MoS₂) has been considered as a promising Pt-substituting electrocatalyst in water splitting for hydrogen evolution reaction (HER). Despite the outstanding HER electrocatalytic performance of MoS₂ in acidic media, it is still a challenge to apply it in alkaline and neutral pH environments. Herein, to expand its application to a wider pH range, modifying the morphology of cobalt (Co) doped bulk MoO_x with a nanorod-array structure to three-dimensional (3D) Co-MoS₂ nanoparticles aggregates was performed via a simple hydrothermal process followed with a sulfidation treatment. By such a simple modification, it is found that the obtained Co-MoS₂ based nickel foam (NF) electrode (Co-MoS₂/NF) can work stably for pH-universal hydrogen evolution with ultra-low overpotentials even at an industrial-level current density of 1000 mA cm⁻², that is, 420 mV at pH = 0, 436 mV at pH = 14 and 870 mV at pH = 7.0. We consider that the incorporation of Co atoms in the MoS₂ framework could optimize the electronic structure of MoS₂ for boosting the HER activity at full pH range, which is inferred by various characterizations including XRD, TEM-EDS, and XPS analyses. It is anticipated that such a Co-MoS₂ electrocatalyst with the 3D Co-MoS₂ nanoparticles aggregates structure could be promising for sustainable and scalable production of hydrogen in various environments.