A flower-like CoS 2 /MoS 2 heteronanosheet array as an active and stable electrocatalyst toward the hydrogen evolution reaction in alkaline media.

CoS 2 /MoS 2 heteronanosheet arrays (HNSAs) with vertically aligned flower-like architectures are fabricated through in situ topotactic sulfurization of CoMoO 4 nanosheet array (NSA) precursors on conductive Ni foam. CoMoO 4 NSAs are prepared by a self-template hydrothermal method without using any hard template and surfactant. Benefiting from a 3D flower-like architecture constituted by ultrathin nanosheets with abundant exposed heterointerfaces as highly active sites and predesigned void spaces, the as-synthesized CoS 2 /MoS 2 HNSAs exhibit an excellent hydrogen evolution reaction (HER) performance with a low overpotential of 50 mV at 10 mA cm -2 , and a small Tafel slope of 76 mV dec -1 in 1.0 M KOH, which outperforms most previously reported CoS 2 and MoS 2 based electrocatalysts with compositional or morphological similarity. This work demonstrates the great potential in developing high-efficiency and earth-abundant electrocatalysts for alkaline HER through heterointerface engineering and morphological design by utilizing transition metal molybdate as a promising platform.