Rational design of high-performance and low-cost electrocatalyst for the hydrogen evolution reaction (HER) is highly desirable but remains a long-standing challenge. Herein, an integration of interfacial engineering and ions incorporation was achieved to develop high-performance hybrid electrocatalyst through a facile phosphidation treatment of Cu2+-doped Co9S8 nanowires arrays (Co9S8-Cu NAs) growth on nickel foam. Through this treatment, cobalt phosphide (CoxP, i.e., Co2P and CoP) nanoparticles are decorated on the surface of Co9S8-Cu NAs, forming a novel ternary CoxP/Co9S8-Cu NAs electrocatalyst. The incorporation of Cu2+ enables the modulation of electronic structures of Co9S8 and contributes to the optimization of reaction immediate energetics. The formed abundant interfaces between CoxP and Co9S8-Cu facilitate the charge transfer and create more exposed active sites, further boosting the HER performance. As a result, the CoPx/Co9S8-Cu NM exhibited high HER activity and stability with a low overpotential of 118 mV to reach a current density of 10 mA cm(-2) in alkaline solution, which can surpass many previously reported Co-based HER catalysts. This work highlights the synergy of the interfacial engineering and ions incorporation in the construction of high-performance and stable electrocatalysts for the water splitting application. (C) 2019 Elsevier Inc. All rights reserved.