Designing new earth-abundant and low-cost catalysts toward the hydrogen evolution reaction (HER) plays a key role in realization of hydrogen economy. In this study, we demonstrate that excellent HER activity is achieved with core-shell Co3O4@CoS2 nanoneedle arrays synthesized by an instantaneous thermal treatment of nanoneedle precursor in H2S atmosphere. The Co3O4@CoS2 structures thus obtained exhibit the current density of 100 mA cm(-2) at a remarkably small overpotential of 210 mV with a small Tafel slope of 45.8 mV decade(-1) in an acidic medium. The outstanding HER performance is achieved particularly from the unique core-shell nanostructure which offers enough electric conductivity and abundant active sites at the grain boundaries and stacking misalignments between two neighbouring cobalt nanostructures. This instantaneous thermal treatment strategy is compatible with the traditional long time sulfur vapor to prepare transition metal chalcogenides with significant hydrogen evolution reaction activities. (C) 2017 Elsevier B.V. All rights reserved.