An efficient nanostructured copper(I) sulfide-based hydrogen evolution electrocatalyst at neutral pH

Developing efficient nonprecious electrocatalysts to accelerate the hydrogen evolution reaction (HER) is of importance for the hydrogen energy technology. Herein, we report the in situ growth of single-crystalline γ-Cu2S nanoplates on copper foam (CF) in a hydrothermal system, with the assistance of a small amount of cobalt(II) acetate. The presence of cobalt(II) acetate in the synthesis system has been proven to have multiple roles: (i) inhibiting the formation of copper(I) oxide (Cu2O); (ii) directing the fromation of the crystal phase of γ-Cu2S; and (iii) controlling the morphology of the as-formed γ-Cu2S. Furthermore, we show that the resulting γ-Cu2S/CF material can serve as an efficient integrated 3D electrode toward HER at neutral pH. The γ-Cu2S/CF delivers a current density of 10 mA/cm2 at a small overpotential of 190 mV, gives 100% Faradaic yield during HER, and maintains its electrocatalytic activity for >10 hours. To the best of our knowledge, this is the first time that a copper(I) sulfide-based material is demonstrated to electrocatalyze the HER efficiently. Identifying copper(I) sulfide as the active phase for HER and constructing advantageous 3D γ-Cu2S nanostructure via an ion-induced method might open a door for the further investigation of Cu-based hydrogen-evolution electrocatalysts.